- Decode errors in LookupArtist/AlbumByMBID now wrap ErrInvalidPayload so
callers can errors.Is the same way they do against the M5a methods.
- Tighten TestLookupAlbumByMBID_BadJSON to assert on ErrInvalidPayload.
- Add empty-mbid rejection tests for both methods.
- Add TestLookupArtistByMBID_EmptyArrayReturnsErrNotFound (only the album
variant had the test before — symmetric coverage now).
- Normalize the network-error test's api key to key123 for consistency
with the rest of delete_test.go.
bvandeusen
dbe0e79f54