fix(lidarr): add an album as the looked-up resource with its artist nested (#5234)

Lidarr's POST /api/v1/album validates `artist` as a nested resource
(AlbumController: RuleFor(s => s.Artist).NotNull()), so the flat payload
we sent was refused with "'Artist' must not be empty" every time. The
album add has never worked against a real Lidarr; approved album and
track requests sat in the reconciler retrying every 5 minutes.

AddAlbum now does what Lidarr's own add-album UI does (getNewAlbum /
getNewArtist): look the album up by MBID (album/lookup?term=lidarr:<mbid>),
then POST that resource back with monitored + searchForNewAlbum. When
Lidarr doesn't have the artist yet, the nested artist gets the request's
quality/metadata profile and root folder, monitors this album only
(monitor "none" + albumsToMonitor, which AlbumMonitoredService prefers)
and no future releases. An artist Lidarr already has is left as it is.
An MBID Lidarr's metadata doesn't know is ErrNotFound with no POST.

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

internal/lidarr/client.go

@@ -324,19 +324,52 @@ func isAlreadyExists(err error) bool {
 		strings.Contains(m, "already in your library")
 }
 
-// AddAlbum posts to POST /api/v1/album. Returns nil on 2xx; typed error
-// otherwise.
+// AddAlbum adds one album to Lidarr the way Lidarr's own UI does: look the
+// album up by MBID, then POST that album resource back with `monitored`,
+// `addOptions` and — when Lidarr doesn't have the artist yet — the
+// artist's profiles, root folder and monitoring filled in.
+//
+// POST /api/v1/album validates `artist` as a nested resource (#5234: a
+// flat payload is refused with "'Artist' must not be empty"), and the
+// lookup is what supplies it: the existing Lidarr artist when there is one,
+// otherwise a new one carrying its metadata. A new artist monitors only
+// this album (monitor "none" with albumsToMonitor, which Lidarr applies in
+// preference to the monitor type) and no future releases, so approving one
+// album never subscribes the library to the artist's whole catalogue.
+//
+// Returns nil on 2xx, ErrAlreadyExists when Lidarr already has the album,
+// ErrNotFound when Lidarr's metadata has no album under that MBID.
 func (c *Client) AddAlbum(ctx context.Context, p AddAlbumParams) error {
-	body, err := json.Marshal(map[string]any{
-		"foreignAlbumId":    p.ForeignAlbumID,
-		"foreignArtistId":   p.ForeignArtistID,
-		"artistName":        p.ArtistName,
-		"qualityProfileId":  p.QualityProfileID,
-		"metadataProfileId": p.MetadataProfileID,
-		"rootFolderPath":    p.RootFolderPath,
-		"monitored":         true,
-		"addOptions":        map[string]any{"searchForNewAlbum": true},
-	})
+	album, err := c.lookupAlbumResource(ctx, p.ForeignAlbumID)
+	if err != nil {
+		return err
+	}
+	album["monitored"] = true
+	album["addOptions"] = map[string]any{"searchForNewAlbum": true}
+
+	artist, _ := album["artist"].(map[string]any)
+	if artist == nil {
+		artist = map[string]any{
+			"foreignArtistId": p.ForeignArtistID,
+			"artistName":      p.ArtistName,
+		}
+		album["artist"] = artist
+	}
+	if id, _ := artist["id"].(float64); id == 0 {
+		artist["qualityProfileId"] = p.QualityProfileID
+		artist["metadataProfileId"] = p.MetadataProfileID
+		artist["rootFolderPath"] = p.RootFolderPath
+		artist["monitored"] = true
+		artist["monitorNewItems"] = "none"
+		artist["addOptions"] = map[string]any{
+			"monitor":                "none",
+			"albumsToMonitor":        []string{p.ForeignAlbumID},
+			"monitored":              true,
+			"searchForMissingAlbums": false,
+		}
+	}
+
+	body, err := json.Marshal(album)
 	if err != nil {
 		return fmt.Errorf("%w: marshal: %v", ErrInvalidPayload, err)
 	}