Four targeted backend tests for behaviour added during the Search/Artists
unification work:
1. _SOURCE_ID_FIELD mapping is parsed out of web_server.py via AST and
compared against an explicit expectation, so silent renames break the
test instead of silently breaking library-upgrade detection.
2. Every column in _SOURCE_ID_FIELD must exist on the real artists table
after migrations run. This is the schema-vs-query contract that the
`deezer_artist_id` typo would have failed instantly.
3. The two queries from the watchlist-config enrichment path execute
verbatim against a fresh DB — separate ones for the artists table
(deezer_id / discogs_id) and the watchlist_artists join (deezer_artist_id).
Documents the column-name split that caused the original bug.
4. Static contract test for _build_source_only_artist_detail's response
shape: every JSON key the frontend reads (success/artist/discography/
image_url/server_source/genres/lastfm_*) must appear in the function
source, plus the dynamic source-id stamp and the dedup_variants=False
opt-out.
Plus a behavioural test for MetadataLookupOptions.dedup_variants=False
in test_metadata_service_discography.py — proves the flag actually keeps
variant releases that get_artist_detail_discography would otherwise
collapse to a single canonical entry.
