Creates internal/musicbrainz/sync.go with SyncArtistDiscography function
that orchestrates the full flow: cache check via GetCachedReleases, fetch
from MusicBrainz API on cache miss, filter via FilterReleaseGroups, and
upsert into external_releases via database.SaveExternalRelease. Includes
SyncArtistDiscographyWithFilter variant for per-artist type filtering. All
functions support context cancellation. 14 new tests cover cache hit/miss,
status/type filtering, context cancellation, idempotency, API errors, and
full XML pipeline integration.
- Add GetArtistReleaseGroups method with pagination support
- Implement status filtering (exclude Bootleg/Promotion/Pseudo-Release)
- Implement type filtering (include Album/Single/EP/Compilation)
- Add per-artist type filtering hooks (ArtistTypeFilter) for Web UI
- Add NormalizeString and NormalizeArtistName for fuzzy matching prep
- Add ReleaseGroup.ToExternalRelease conversion method
- Write comprehensive table-driven tests for filtering logic
- Write tests for normalization functions (18 cases)
- Write tests for GetArtistReleaseGroups (success, pagination, empty, errors)
- All tests pass (47 total across project), go vet clean
