Clicking a MusicBrainz album returned 404 because the browse-based
search path now stores release-GROUP MBIDs in Album.id, but `get_album`
still hit `/ws/2/release/<mbid>` directly. Release-group MBIDs don't
resolve as release MBIDs — MB 404s. User log:
GET /api/spotify/album/b88655ba...?source=musicbrainz → 404
Error fetching release b88655ba...: 404 Client Error
The fix requires a two-step resolution for the new browse path:
1. Look up the release-group with `inc=releases+artist-credits` to get
the list of releases inside (original + reissues + regional + promo
editions). MB release-groups routinely hold 5-20 releases.
2. Pick a representative release: prefer Official status over Promo,
prefer releases with a real tracklist over stubs, then earliest date.
3. Fetch that release's full tracklist via `get_release`.
Two extra seconds at the 1-rps rate limit, but it's on click, not on
search results rendering.
Structure:
- New `MusicBrainzClient.get_release_group(mbid, includes)` method.
- New `_pick_representative_release(releases)` helper encapsulates the
ranking logic.
- Tracklist projection extracted into `_render_release_as_album` so
both paths share the same shape construction.
- `get_album` tries release-group first; falls back to direct release
lookup when the MBID turns out to be a release from the text-search
fallback path.
- Canonical Album.id stays the release-group MBID so a re-fetch with
the same URL hits the same code path idempotently.
3 new tests (now 33 total):
- End-to-end release-group → release resolution with mocked client
- Fallback to direct release lookup when rg lookup misses
- Representative-release picker ranks correctly
Verified against live API with the exact MBID that 404'd for the user
(b88655ba... for DAMN. by Kendrick Lamar): now returns in 1.2s with
the full 14-track listing (BLOOD., DNA., YAH., ELEMENT., FEEL., ...).