Milestone #160 Option 1, Step 2. New internal/tags package that enriches
the taste profile's tag facet beyond raw ID3 genre, built so adding a
source later is "implement TrackTagProvider + Register()" — no enricher,
settings, or schema change (operator directive).
Mirrors the internal/coverart pattern:
- Provider interface + package registry (Register/AllProviders/ByID);
TrackTagProvider fetch capability + TestableProvider for the admin test.
- DB-backed SettingsService over new tag_provider_settings +
tag_sources_meta (migration 0043) — enable/key/version, boot
reconciliation, and a provider-hash bump that re-opens 'none' rows when
the compiled-in provider set changes.
- Slim self-contained httpClient (rate-limit + retry + User-Agent), kept
local so tag enrichment never depends on coverart internals.
Providers:
- MusicBrainz: keyless, default-ON, recording tags by MBID (rule #26 baseline).
- Last.fm: keyed, default-OFF, track.getTopTags by artist+track — opt-in
once a key is supplied.
Enricher uses MERGE semantics (differs from coverart's first-success-wins
for a single image): unions tags across every enabled provider, caps to
top-K by weight, and stamps tag_source musicbrainz|lastfm|mixed|none.
Writes are transactional (atomic replace of track_tags).
Unit-tested without a DB: registry mechanics, provider JSON parsing +
weight normalization via httptest, and the pure merge/top-K/source-label
helpers. Wiring (startup + on-scan), integration tests, and the taste
union (Step 3) + Settings UI (Step 4) come next.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>