merge trails function added (#627)

* merge trails function added

* fix conflict resolve issues

* avoid incorrect authorship when merging trail comments

* require edit access for all selected trails before merge

* fix likes checkbox binding in trail merge modal

* improve error handling

* require editable target and deletable sources for merge

* avoid duplicate trail fetch during merge

* prevent duplicate likes when merging trails

* check photo download responses during trail merge

* add merge completion toast notifications

* cleanup

* small fixes

* move merge code to backend, option to merge single trail selection with similar one, automatic merge for integrations add as option, maintenance page to find and merge similar trails added

* fix build error

* fix

* docu, beautifying, refactoring

---------

Co-authored-by: Flomp <Flomp@users.noreply.github.com>

db/trailmerge/integration_merge.go

@@ -0,0 +1,44 @@
+package trailmerge
+
+import (
+	"github.com/meilisearch/meilisearch-go"
+	"github.com/pocketbase/pocketbase/core"
+)
+
+func TryAutoMergeImportedTrail(
+	app core.App,
+	client meilisearch.ServiceManager,
+	actor *core.Record,
+	sourceTrailID string,
+	settings IntegrationAutoMergeSettings,
+) error {
+	if actor == nil || sourceTrailID == "" || !settings.Enabled {
+		return nil
+	}
+
+	response, err := Suggest(app, actor.Id, SuggestRequest{
+		Mode:          SuggestModeAutoDiscovery,
+		SourceTrailID: sourceTrailID,
+	})
+	if err != nil {
+		return err
+	}
+
+	selectableCandidates := make([]SuggestCandidate, 0, len(response.Candidates))
+	for _, candidate := range response.Candidates {
+		if candidate.Selectable {
+			selectableCandidates = append(selectableCandidates, candidate)
+		}
+	}
+
+	if len(selectableCandidates) != 1 {
+		return nil
+	}
+
+	targetTrailID := selectableCandidates[0].TrailID
+	if targetTrailID == "" || targetTrailID == sourceTrailID {
+		return nil
+	}
+
+	return Merge(app, client, actor, sourceTrailID, targetTrailID, DefaultIntegrationAutoMergeMergeSettings())
+}