Added CODE_CONVENTIONS.md and linters to enforce it, and applied it across the codebase

CODE_CONVENTIONS.md sets out the conventions for Go code in this
repository: naming, layout, comments, errors, logging, configuration and
tests. .golangci.json enables the linters that check the parts that can be
checked (each limited to the rules the conventions use); the rest is
applied by hand.

Applied across the codebase:
- Naming: full-word names in application code, initialisms in one case
  (BuyerID, PrintJSON, PrintYAML, ocdsGetBuyerID), no names shadowing
  built-ins (min/max are minGap/maxGap), mustRaw renamed rawJSON as it
  returns nil rather than panicking, and config.ConfigLevelToLogLevel
  renamed LevelToLogLevel.
- Layout: lines kept to 80 characters where possible, assignments taken
  out of if and for statements that don't fit, wrapped arguments all on
  one line or one per line, steps separated by blank lines, no else after
  a return, function and struct literals wrapped.
- Comments: doc comments on every exported name (including each section's
  Map, Flatten, TypeOf, ValueOf and SetValue), section banners, British
  spelling.
- Errors: a created error starts with its package name, a wrapping error
  adds only what was being done, sentinels in one commented var block,
  errors.Is and errors.As in place of == and type assertions, and no
  err := shadowing of a named result. That fixes the mock server losing
  its access log's close error.
- Logging: the fetcher passes its workers an untagged logger, so
  findatender's lines are tagged with their own component rather than
  with fetcher's as well; cmd/mock-fts logs "stopped" with slog.
- Configuration: util.WithTimeout (moved from the websocket package)
  applies a timeout of 0 or less as no limit, used for the websocket
  write and ping, TCP close and tcpserver shutdown timeouts; every setting
  documents what 0 or empty means, including the rate limit rule's keys
  in internal/config/README.md.
- Tests: related tests merged into table-driven ones with named cases.

Separately from CODE_CONVENTIONS.md, internal/store/README.md gains a soft
SQL style convention for the queries in internal/store/queries.go, and the
queries are reformatted to follow it.

internal/store/store_test.go

@@ -30,7 +30,11 @@ func day(d int) time.Time {
 	return time.Date(2026, time.March, d, 9, 30, 0, 0, time.UTC)
 }
 
-func opportunity(uuid, title string, releaseDay int, releaseIDs ...string) *types.Opportunity {
+func opportunity(
+	uuid, title string,
+	releaseDay int,
+	releaseIDs ...string,
+) *types.Opportunity {
 	start, end := day(20), day(28)
 	t := &types.Opportunity{
 		UUID:              uuid,
@@ -39,7 +43,7 @@ func opportunity(uuid, title string, releaseDay int, releaseIDs ...string) *type
 		Status:            "active",
 		Description:       "A description",
 		BuyerName:         "Example Council",
-		BuyerId:           "GB-EXAMPLE",
+		BuyerID:           "GB-EXAMPLE",
 		MainCategory:      "services",
 		ProcurementMethod: "open",
 		MultiLot:          true,
@@ -49,8 +53,16 @@ func opportunity(uuid, title string, releaseDay int, releaseIDs ...string) *type
 		GrossValue:        125000.50,
 		HasDocuments:      true,
 		Classifications: []types.ClassificationCode{
-			{IsCPV: true, Code: "72000000", Classification: "IT services"},
-			{IsCPV: true, Code: "03000000", Classification: "Agricultural products"},
+			{
+				IsCPV:          true,
+				Code:           "72000000",
+				Classification: "IT services",
+			},
+			{
+				IsCPV:          true,
+				Code:           "03000000",
+				Classification: "Agricultural products",
+			},
 		},
 		// No UUID: SaveOpportunity must fill it in.
 		Marks: types.OpportunityMarks{
@@ -58,18 +70,29 @@ func opportunity(uuid, title string, releaseDay int, releaseIDs ...string) *type
 			BidSubmitted: true,
 		},
 	}
+
 	for i, id := range releaseIDs {
 		t.Releases = append(t.Releases, types.OpportunityRelease{
 			ReleaseID:   id,
 			ReleaseDate: day(releaseDay).Add(time.Duration(i) * time.Minute),
 			JSON:        `{"id":"` + id + `"}`,
-			Tags:        []types.OpportunityReleaseTag{{Tag: "opportunity"}, {Tag: "planning"}},
+			Tags: []types.OpportunityReleaseTag{
+				{
+					Tag: "opportunity",
+				},
+				{
+					Tag: "planning",
+				},
+			},
 		})
 	}
+
 	return t
 }
 
-func mustSave(t *testing.T, s *store.Store, td *types.Opportunity) store.SaveResult {
+func mustSave(
+	t *testing.T, s *store.Store, td *types.Opportunity,
+) store.SaveResult {
 	t.Helper()
 	res, err := s.SaveOpportunity(context.Background(), td)
 	if err != nil {
@@ -116,24 +139,30 @@ func TestSaveAndGetRoundTrip(t *testing.T) {
 	}
 
 	got := mustGet(t, s, "ocds-1")
-	if got.Title != in.Title || got.BuyerName != in.BuyerName || got.BuyerId != in.BuyerId ||
-		got.MainCategory != in.MainCategory || got.ProcurementMethod != in.ProcurementMethod ||
-		got.UUIDType != "ocid" || got.Status != "active" || got.Description != in.Description ||
-		!got.MultiLot || !got.SMESuitable || got.VCSESuitable || !got.HasDocuments ||
-		got.GrossValue != in.GrossValue {
+	if got.Title != in.Title || got.BuyerName != in.BuyerName ||
+		got.BuyerID != in.BuyerID || got.MainCategory != in.MainCategory ||
+		got.ProcurementMethod != in.ProcurementMethod || got.UUIDType != "ocid" ||
+		got.Status != "active" || got.Description != in.Description ||
+		!got.MultiLot || !got.SMESuitable || got.VCSESuitable ||
+		!got.HasDocuments || got.GrossValue != in.GrossValue {
 		t.Errorf("opportunity fields differ:\n got %+v\nwant %+v", got, in)
 	}
-	if got.StartDate == nil || !got.StartDate.Equal(day(20)) || got.EndDate == nil ||
-		!got.EndDate.Equal(day(28)) {
+	if got.StartDate == nil || !got.StartDate.Equal(day(20)) ||
+		got.EndDate == nil || !got.EndDate.Equal(day(28)) {
 		t.Errorf("dates: got %v / %v", got.StartDate, got.EndDate)
 	}
 	if want := day(1).Add(time.Minute); !got.LatestReleaseDate.Equal(want) {
 		t.Errorf("LatestReleaseDate = %v, want %v", got.LatestReleaseDate, want)
 	}
 
-	if len(got.Classifications) != 2 || got.Classifications[0].Code != "03000000" ||
-		got.Classifications[1].Code != "72000000" || got.Classifications[0].ID == 0 {
-		t.Errorf("classifications: got %+v (leading zero must survive)", got.Classifications)
+	if len(got.Classifications) != 2 ||
+		got.Classifications[0].Code != "03000000" ||
+		got.Classifications[1].Code != "72000000" ||
+		got.Classifications[0].ID == 0 {
+		t.Errorf(
+			"classifications: got %+v (leading zero must survive)",
+			got.Classifications,
+		)
 	}
 
 	wantMarks := types.OpportunityMarks{
@@ -153,9 +182,8 @@ func TestSaveAndGetRoundTrip(t *testing.T) {
 		!r.ReleaseDate.Equal(day(1)) {
 		t.Errorf("release: got %+v", r)
 	}
-	if len(r.Tags) != 2 ||
-		r.Tags[0].Tag != "opportunity" || r.Tags[1].Tag != "planning" ||
-		r.Tags[0].ReleaseID != "r1" ||
+	if len(r.Tags) != 2 || r.Tags[0].Tag != "opportunity" ||
+		r.Tags[1].Tag != "planning" || r.Tags[0].ReleaseID != "r1" ||
 		r.Tags[0].UUID != "ocds-1" {
 		t.Errorf("tags: got %+v", r.Tags)
 	}
@@ -178,7 +206,9 @@ func TestReleasesAreWriteOnce(t *testing.T) {
 
 	again := opportunity("ocds-1", "Title", 1, "r1")
 	again.Releases[0].JSON = `{"changed":true}`
-	again.Releases[0].Tags = []types.OpportunityReleaseTag{{Tag: "award"}}
+	again.Releases[0].Tags = []types.OpportunityReleaseTag{{
+		Tag: "award",
+	}}
 	if res := mustSave(t, s, again); res.NewReleases != 0 {
 		t.Errorf("re-save: NewReleases = %d, want 0", res.NewReleases)
 	}
@@ -206,7 +236,9 @@ func TestOlderReleaseDoesNotOverwriteOpportunity(t *testing.T) {
 		t.Errorf("opportunity was overwritten by an older release: %+v", got)
 	}
 	if len(got.Releases) != 2 || got.Releases[0].ReleaseID != "r1" {
-		t.Errorf("older release should still be stored, oldest first: %+v", got.Releases)
+		t.Errorf(
+			"older release should still be stored, oldest first: %+v", got.Releases,
+		)
 	}
 }
 
@@ -220,7 +252,11 @@ func TestNewerReleaseUpdatesOpportunityAndSearchIndex(t *testing.T) {
 	newer := opportunity("ocds-1", "Website redesign", 2, "r2")
 	newer.Status = "complete"
 	newer.Classifications = []types.ClassificationCode{
-		{IsCPV: true, Code: "72000000", Classification: "IT services (amended)"},
+		{
+			IsCPV:          true,
+			Code:           "72000000",
+			Classification: "IT services (amended)",
+		},
 	}
 	if res := mustSave(t, s, newer); !res.OpportunityUpdated {
 		t.Fatalf("newer save not applied: %+v", res)
@@ -246,7 +282,12 @@ func TestNewerReleaseUpdatesOpportunityAndSearchIndex(t *testing.T) {
 			t.Fatal(err)
 		}
 		if len(ts) != want {
-			t.Errorf("search %q after title change: %d results, want %d", title, len(ts), want)
+			t.Errorf(
+				"search %q after title change: %d results, want %d",
+				title,
+				len(ts),
+				want,
+			)
 		}
 	}
 }
@@ -257,7 +298,8 @@ func TestClassificationRowsAreShared(t *testing.T) {
 	b := opportunity("ocds-b", "B", 1, "r1")
 	mustSave(t, s, a)
 	mustSave(t, s, b)
-	if a.Classifications[0].ID == 0 || a.Classifications[0].ID != b.Classifications[0].ID {
+	if a.Classifications[0].ID == 0 ||
+		a.Classifications[0].ID != b.Classifications[0].ID {
 		t.Errorf(
 			"identical classifications should share an ID: %d vs %d",
 			a.Classifications[0].ID,
@@ -267,7 +309,11 @@ func TestClassificationRowsAreShared(t *testing.T) {
 
 	c := opportunity("ocds-c", "C", 1, "r1")
 	c.Classifications = []types.ClassificationCode{
-		{IsCPV: false, Code: "72000000", Classification: "IT services"},
+		{
+			IsCPV:          false,
+			Code:           "72000000",
+			Classification: "IT services",
+		},
 	}
 	mustSave(t, s, c)
 	if c.Classifications[0].ID == a.Classifications[0].ID {
@@ -279,13 +325,17 @@ func TestSameReleaseIDInDifferentOpportunities(t *testing.T) {
 	s := openStore(t)
 	a := opportunity("ocds-a", "A", 1, "001")
 	b := opportunity("ocds-b", "B", 1, "001")
-	b.Releases[0].Tags = []types.OpportunityReleaseTag{{Tag: "award"}}
+	b.Releases[0].Tags = []types.OpportunityReleaseTag{{
+		Tag: "award",
+	}}
+
 	if res := mustSave(t, s, a); res.NewReleases != 1 {
 		t.Fatal(res)
 	}
 	if res := mustSave(t, s, b); res.NewReleases != 1 {
 		t.Fatalf("release id reused under another OCID must be stored: %+v", res)
 	}
+
 	got := mustGet(t, s, "ocds-b").Releases
 	if len(got) != 1 || len(got[0].Tags) != 1 || got[0].Tags[0].Tag != "award" {
 		t.Errorf("tags leaked between opportunities: %+v", got)
@@ -300,7 +350,11 @@ func TestListOpportunitiesFilters(t *testing.T) {
 	roads := opportunity("ocds-2", "Road resurfacing works", 2, "r1")
 	roads.Status = "complete"
 	roads.Classifications = []types.ClassificationCode{
-		{IsCPV: true, Code: "45233142", Classification: "Road-repair works"},
+		{
+			IsCPV:          true,
+			Code:           "45233142",
+			Classification: "Road-repair works",
+		},
 	}
 	hosting := opportunity("ocds-3", "Managed cloud hosting", 3, "r1")
 	for _, td := range []*types.Opportunity{cloud, roads, hosting} {
@@ -312,7 +366,11 @@ func TestListOpportunitiesFilters(t *testing.T) {
 		f    store.OpportunityFilter
 		want []string
 	}{
-		{"all, newest first", store.OpportunityFilter{}, []string{"ocds-3", "ocds-2", "ocds-1"}},
+		{
+			"all, newest first",
+			store.OpportunityFilter{},
+			[]string{"ocds-3", "ocds-2", "ocds-1"},
+		},
 		{"status", store.OpportunityFilter{
 			Status: "complete",
 		}, []string{"ocds-2"}},
@@ -385,9 +443,13 @@ func TestListOpportunitiesFilters(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(got) != 1 || len(got[0].Classifications) != 1 || got[0].Releases != nil ||
-		got[0].Marks.UUID != "ocds-2" || !got[0].Marks.Interested {
-		t.Errorf("list should include classifications and marks and omit releases: %+v", got)
+	if len(got) != 1 || len(got[0].Classifications) != 1 ||
+		got[0].Releases != nil || got[0].Marks.UUID != "ocds-2" ||
+		!got[0].Marks.Interested {
+		t.Errorf(
+			"list should include classifications and marks and omit releases: %+v",
+			got,
+		)
 	}
 }
 
@@ -402,26 +464,28 @@ func TestReleaseExistsAndListReleases(t *testing.T) {
 	}{{"ocds-1", "r1", true}, {"ocds-1", "r3", false}, {"ocds-2", "r1", false}} {
 		got, err := s.ReleaseExists(ctx, tc.uuid, tc.id)
 		if err != nil || got != tc.want {
-			t.Errorf("ReleaseExists(%s, %s) = %v, %v; want %v", tc.uuid, tc.id, got, err, tc.want)
+			t.Errorf(
+				"ReleaseExists(%s, %s) = %v, %v; want %v",
+				tc.uuid,
+				tc.id,
+				got,
+				err,
+				tc.want,
+			)
 		}
 	}
 
 	rs, err := s.ListReleases(ctx, "ocds-1")
-	if err != nil || len(rs) != 2 || rs[0].ReleaseID != "r1" || rs[1].ReleaseID != "r2" ||
-		len(rs[1].Tags) != 2 {
+	if err != nil || len(rs) != 2 || rs[0].ReleaseID != "r1" ||
+		rs[1].ReleaseID != "r2" || len(rs[1].Tags) != 2 {
 		t.Errorf("ListReleases: %+v, %v", rs, err)
 	}
 }
 
 func TestGetOpportunityNotFound(t *testing.T) {
 	s := openStore(t)
-	if _, err := s.GetOpportunity(
-		context.Background(),
-		"missing",
-	); !errors.Is(
-		err,
-		store.ErrNotFound,
-	) {
+	_, err := s.GetOpportunity(context.Background(), "missing")
+	if !errors.Is(err, store.ErrNotFound) {
 		t.Errorf("err = %v, want ErrNotFound", err)
 	}
 }
@@ -473,8 +537,12 @@ func TestResaveLoadedOpportunity(t *testing.T) {
 	ids := []int64{loaded.Classifications[0].ID, loaded.Classifications[1].ID}
 	loaded.Title = "Amended"
 	loaded.Releases = append(loaded.Releases, types.OpportunityRelease{
-		ReleaseID: "r2", ReleaseDate: day(2), JSON: `{}`,
-		Tags: []types.OpportunityReleaseTag{{Tag: "opportunityAmendment"}},
+		ReleaseID:   "r2",
+		ReleaseDate: day(2),
+		JSON:        `{}`,
+		Tags: []types.OpportunityReleaseTag{{
+			Tag: "opportunityAmendment",
+		}},
 	})
 	res := mustSave(t, s, loaded)
 	if !res.OpportunityUpdated || res.NewReleases != 1 {
@@ -482,10 +550,12 @@ func TestResaveLoadedOpportunity(t *testing.T) {
 	}
 
 	got := mustGet(t, s, "ocds-1")
-	if got.Title != "Amended" || len(got.Releases) != 2 || !got.LatestReleaseDate.Equal(day(2)) {
+	if got.Title != "Amended" || len(got.Releases) != 2 ||
+		!got.LatestReleaseDate.Equal(day(2)) {
 		t.Errorf("resave not applied: %+v", got)
 	}
-	if got.Classifications[0].ID != ids[0] || got.Classifications[1].ID != ids[1] {
+	if got.Classifications[0].ID != ids[0] ||
+		got.Classifications[1].ID != ids[1] {
 		t.Errorf(
 			"classification IDs changed on resave: %v -> %d, %d",
 			ids,
@@ -527,10 +597,7 @@ func TestSetMarksErrors(t *testing.T) {
 			UUID:   "missing",
 			Hidden: true,
 		},
-	); !errors.Is(
-		err,
-		store.ErrNotFound,
-	) {
+	); !errors.Is(err, store.ErrNotFound) {
 		t.Errorf("unknown opportunity: err = %v, want ErrNotFound", err)
 	}
 	if err := s.SetMarks(ctx, types.OpportunityMarks{
@@ -565,7 +632,9 @@ func TestSaveKeepsExistingMarks(t *testing.T) {
 
 	newest := opportunity("ocds-1", "Amended again", 3, "r3")
 	newest.Marks = types.OpportunityMarks{}
-	if _, err := s.SaveOpportunities(ctx, []*types.Opportunity{newest}); err != nil {
+	if _, err := s.SaveOpportunities(
+		ctx, []*types.Opportunity{newest},
+	); err != nil {
 		t.Fatal(err)
 	}
 	if got := mustGet(t, s, "ocds-1").Marks; got != want {
@@ -580,9 +649,13 @@ func TestSaveOpportunitiesStoresMarks(t *testing.T) {
 	b.Marks = types.OpportunityMarks{
 		Skipped: true,
 	}
-	if _, err := s.SaveOpportunities(context.Background(), []*types.Opportunity{a, b}); err != nil {
+
+	if _, err := s.SaveOpportunities(
+		context.Background(), []*types.Opportunity{a, b},
+	); err != nil {
 		t.Fatal(err)
 	}
+
 	for uuid, want := range map[string]types.OpportunityMarks{
 		"ocds-a": {UUID: "ocds-a", Interested: true, BidSubmitted: true},
 		"ocds-b": {UUID: "ocds-b", Skipped: true},
@@ -610,7 +683,10 @@ func TestListOpportunitiesMarkFilters(t *testing.T) {
 		Lost:    true,
 	})
 	mustSetMarks(t, s, types.OpportunityMarks{
-		UUID: "ocds-4", Interested: true, BidSubmitted: true, Won: true,
+		UUID:         "ocds-4",
+		Interested:   true,
+		BidSubmitted: true,
+		Won:          true,
 	})
 
 	set, unset := store.MarkSet, store.MarkUnset
@@ -619,7 +695,11 @@ func TestListOpportunitiesMarkFilters(t *testing.T) {
 		f    store.OpportunityFilter
 		want []string
 	}{
-		{"any", store.OpportunityFilter{}, []string{"ocds-4", "ocds-3", "ocds-2", "ocds-1"}},
+		{
+			"any",
+			store.OpportunityFilter{},
+			[]string{"ocds-4", "ocds-3", "ocds-2", "ocds-1"},
+		},
 		{"hidden", store.OpportunityFilter{
 			Hidden: set,
 		}, []string{"ocds-2"}},
@@ -698,8 +778,8 @@ func TestListOpportunitiesMarkFilters(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(got) != 4 || !got[0].Marks.Won || !got[1].Marks.Lost || !got[2].Marks.Hidden ||
-		got[3].Marks.Hidden || !got[3].Marks.Interested {
+	if len(got) != 4 || !got[0].Marks.Won || !got[1].Marks.Lost ||
+		!got[2].Marks.Hidden || got[3].Marks.Hidden || !got[3].Marks.Interested {
 		t.Errorf("list marks: %+v", got)
 	}
 }
@@ -727,19 +807,20 @@ func TestWonAndLostAreExclusive(t *testing.T) {
 		Won:  true,
 		Lost: true,
 	}
-	if _, err := s.SaveOpportunity(ctx, in); !errors.Is(err, types.ErrWonAndLost) {
+	_, err := s.SaveOpportunity(ctx, in)
+	if !errors.Is(err, types.ErrWonAndLost) {
 		t.Errorf("SaveOpportunity(won and lost): err = %v, want ErrWonAndLost", err)
 	}
-	if _, err := s.SaveOpportunities(
-		ctx,
-		[]*types.Opportunity{in},
-	); !errors.Is(
-		err,
-		types.ErrWonAndLost,
-	) {
-		t.Errorf("SaveOpportunities(won and lost): err = %v, want ErrWonAndLost", err)
+
+	_, err = s.SaveOpportunities(ctx, []*types.Opportunity{in})
+	if !errors.Is(err, types.ErrWonAndLost) {
+		t.Errorf(
+			"SaveOpportunities(won and lost): err = %v, want ErrWonAndLost", err,
+		)
 	}
-	if _, err := s.GetOpportunity(ctx, "ocds-2"); !errors.Is(err, store.ErrNotFound) {
+
+	_, err = s.GetOpportunity(ctx, "ocds-2")
+	if !errors.Is(err, store.ErrNotFound) {
 		t.Errorf("rejected opportunity was stored: err = %v", err)
 	}