Made the fetcher save what it fetches, with fetcher.WithStore

With WithStore, the Find a Tender and mock workers save each run's
opportunities with SaveOpportunities and log what changed; a failed save
fails the run, so the checkpoint stays put and the next run retries.
Without a store nothing is persisted. The mock's opportunities are saved
with Source "FTSMock" rather than the converter's "FindATender".

fetcher service and job-search serve open the store at database.file
(cli.OpenConfiguredStore), or warn and run without one. A missing file
isn't created, and a database needing migration says to run job-search
migrate.

Fixed upsertOpportunity, which never wrote the source column, so every
saved opportunity had an empty Source.

internal/store/queries.go

@@ -32,13 +32,13 @@ const upsertOpportunity = `
 INSERT INTO opportunities (
 	uuid, uuid_type, title, status, description, buyer_name, buyer_id,
 	main_category, procurement_method, multi_lot, sme_suitable,
-	vcse_suitable, start_date, end_date, gross_value, has_documents,
+	vcse_suitable, start_date, end_date, gross_value, has_documents, source,
 	latest_release_date
 ) VALUES (
 	:uuid, :uuid_type, :title, :status, :description, :buyer_name, :buyer_id,
 	:main_category, :procurement_method, :multi_lot, :sme_suitable,
 	:vcse_suitable, :start_date, :end_date, :gross_value, :has_documents,
-	:latest_release_date
+	:source, :latest_release_date
 )
 ON CONFLICT (uuid) DO UPDATE SET
 	uuid_type = excluded.uuid_type,
@@ -56,6 +56,7 @@ ON CONFLICT (uuid) DO UPDATE SET
 	end_date = excluded.end_date,
 	gross_value = excluded.gross_value,
 	has_documents = excluded.has_documents,
+	source = excluded.source,
 	latest_release_date = excluded.latest_release_date`
 
 // selectOpportunityByUUID reads one opportunity into a opportunityRow.

internal/store/store_test.go

@@ -52,6 +52,7 @@ func opportunity(
 		EndDate:           &end,
 		GrossValue:        125000.50,
 		HasDocuments:      true,
+		Source:            "FindATender",
 		Classifications: []types.ClassificationCode{
 			{
 				IsCPV:          true,
@@ -144,7 +145,8 @@ func TestSaveAndGetRoundTrip(t *testing.T) {
 		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 {
+		!got.HasDocuments || got.GrossValue != in.GrossValue ||
+		got.Source != in.Source {
 		t.Errorf("opportunity fields differ:\n got %+v\nwant %+v", got, in)
 	}
 	if got.StartDate == nil || !got.StartDate.Equal(day(20)) ||