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/fetcher/fetcher.go

@@ -9,6 +9,8 @@ import (
 	"time"
 
 	"git.avsdev.uk/Go/job-search/internal/config"
+	"git.avsdev.uk/Go/job-search/internal/store"
+	"git.avsdev.uk/Go/job-search/internal/types"
 	"git.avsdev.uk/Go/job-search/internal/util"
 )
 
@@ -27,6 +29,21 @@ func WithLogger(logger *slog.Logger) Option {
 	}
 }
 
+// WithStore makes the workers save the opportunities they fetch to
+// opportunityStore. Without it, nothing is persisted.
+func WithStore(opportunityStore *store.Store) Option {
+	return func(f *Fetcher) {
+		f.store = opportunityStore
+	}
+}
+
+// saveFunc saves the opportunities a worker fetched; see Fetcher.save.
+type saveFunc func(
+	ctx context.Context,
+	logger *slog.Logger,
+	opportunities []*types.Opportunity,
+) error
+
 // logger returns the logger Run logs to: the given one, or slog.Default().
 // It isn't tagged here, as it is also given to the clients the workers
 // create, which add their own component; see tagged.
@@ -48,6 +65,7 @@ func tagged(logger *slog.Logger) *slog.Logger {
 type Fetcher struct {
 	conf    *config.JSCSources
 	log     *slog.Logger
+	store   *store.Store // nil: nothing is persisted
 	started time.Time
 
 	// backgroundCtx is the context the workers run under. backgroundCancel
@@ -119,12 +137,12 @@ func (f *Fetcher) Run(ctx context.Context, since time.Time) error {
 
 	if f.conf.FindATender.Enabled {
 		start("FindATender", func(ctx context.Context) error {
-			return runFindATender(ctx, logger, &f.conf.FindATender, since)
+			return runFindATender(ctx, logger, &f.conf.FindATender, f.save, since)
 		})
 	}
 	if f.conf.FTSMock.Enabled {
 		start("FTSMock", func(ctx context.Context) error {
-			return runFTSMock(ctx, logger, &f.conf.FTSMock, since)
+			return runFTSMock(ctx, logger, &f.conf.FTSMock, f.save, since)
 		})
 	}
 	if f.conf.Sleeper.Enabled {
@@ -139,3 +157,30 @@ func (f *Fetcher) Run(ctx context.Context, since time.Time) error {
 
 	return errors.Join(errs...)
 }
+
+// save saves opportunities to the store given WithStore, and logs what
+// changed. Without a store it does nothing. A failure fails the worker's run,
+// so its checkpoint isn't moved on and the next run fetches them again.
+func (f *Fetcher) save(
+	ctx context.Context,
+	logger *slog.Logger,
+	opportunities []*types.Opportunity,
+) error {
+	if f.store == nil {
+		return nil
+	}
+
+	result, err := f.store.SaveOpportunities(ctx, opportunities)
+	if err != nil {
+		return fmt.Errorf("saving opportunities: %w", err)
+	}
+
+	tagged(logger).Info(
+		"saved opportunities",
+		"new_opportunities", result.NewOpportunities,
+		"updated_opportunities", result.UpdatedOpportunities,
+		"new_releases", result.NewReleases,
+	)
+
+	return nil
+}