feat(notifications): requests and flags reach the people who act on them (#5340)

- A new request still pending after any auto-approval notifies the
  admins (request_pending), but not the requester if they are an admin.
  A request that dedups into one already in flight is not announced again.
- Approving or rejecting a request notifies the requester, and a
  rejection carries the admin's notes as the reason. An admin deciding
  their own request gets nothing.
- The reconciler notifies the requester when their request arrives
  (request_completed), linking the matched album or artist.
- A request the re-acquisition sweeper files and cannot approve itself
  notifies the admins.
- A quarantine flag notifies every admin except the flagger, naming the
  track, the flagger and the reason.

lidarrrequests.Service.CreateTracked reports whether a request was
inserted or deduped; Create wraps it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/notify_producers.go

@@ -0,0 +1,73 @@
+package api
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrrequests"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/notifications"
+)
+
+// Helpers for the handlers that produce notifications (M489). Every call is
+// NotifyLogged: a notification never fails the action that caused it.
+
+// userLabel is how a user is named to someone else: their display name, or
+// their username when they have none.
+func userLabel(u dbq.User) string {
+	if u.DisplayName != nil && *u.DisplayName != "" {
+		return *u.DisplayName
+	}
+	return u.Username
+}
+
+func requestPayload(row dbq.LidarrRequest) notifications.Payload {
+	return notifications.Payload{
+		RequestID:   uuidToString(row.ID),
+		RequestKind: string(row.Kind),
+		Name:        lidarrrequests.DisplayName(row),
+	}
+}
+
+// notifyRequestDecided tells the requester an admin approved or declined
+// their request. An admin deciding their own request needs no notice.
+func (h *handlers) notifyRequestDecided(ctx context.Context, kind notifications.Kind, admin dbq.User, row dbq.LidarrRequest, reason string) {
+	if row.UserID == admin.ID {
+		return
+	}
+	p := requestPayload(row)
+	p.Reason = reason
+	h.notifier.NotifyLogged(ctx, kind, notifications.ToUser(row.UserID), p.Map())
+}
+
+// quarantineReasonLabel is a flag reason as the flag popover words it, in
+// lower case to sit inside a sentence ("flagged X: bad rip").
+func quarantineReasonLabel(reason string) string {
+	switch reason {
+	case "bad_rip":
+		return "bad rip"
+	case "wrong_file":
+		return "wrong file"
+	case "wrong_tags":
+		return "wrong tags"
+	case "duplicate":
+		return "duplicate"
+	default:
+		return ""
+	}
+}
+
+// trackLabel names a track "Artist – Title" for a notification, falling back
+// to the title alone, or to nothing, rather than failing the caller.
+func (h *handlers) trackLabel(ctx context.Context, trackID pgtype.UUID) string {
+	q := dbq.New(h.pool)
+	t, err := q.GetTrackByID(ctx, trackID)
+	if err != nil {
+		return ""
+	}
+	if a, aerr := q.GetArtistByID(ctx, t.ArtistID); aerr == nil && a.Name != "" {
+		return a.Name + " – " + t.Title
+	}
+	return t.Title
+}