CMRT 21: Worker: Retrieve all four MBID fields from AcoustID in one request

[Swarnadip-Kar]

Resolves the three hardcoded QString() placeholders in acoustidResultReady
and the "requires a separate MusicBrainz call" TODO. All four MBID fields
now come from the single AcoustID /v2/lookup response with no extra
network calls.

Changes

acoustidworker.h

• LookupResult gains releaseId, artistId, trackId string members.
  All default to QString(). Comments document the JSON path each
  field is extracted from.

acoustidworker.cpp — doLookup()

• meta parameter: "recordingids" → "recordings releases tracks"
• JSON parsing: existing recording UUID loop unchanged. New block
  after it descends into recordings[0].releases[0] for releaseId and
  artistId, and into releases[0].mediums[0].tracks[0] for trackId.
  Every array level is guarded with isEmpty() — the API omits arrays
  entirely when empty rather than returning [].

acoustidworker.cpp — processJob() Step 5a

• cacheEntry.musicbrainzReleaseId populated from result.releaseId so
  cache hits also carry the release field for audio-duplicate tracks.
• emit acoustidResultReady: three QString() replaced with
  result.releaseId, result.trackId, result.artistId.

Notes for reviewers

• The guard at every array level (recordings, releases, artists,
  mediums, tracks) is required. The AcoustID API contract omits arrays
  entirely when they are empty — a missing key returns QJsonValue::Undefined
  and .toArray() returns an empty QJsonArray, which isEmpty() catches.
  Skipping any guard would crash on tracks with partial metadata coverage.
• Only the first recording, first release, first artist, and first track
  are used — consistent with how we already take the first recording UUID
  for the recording ID.
• The cache write now includes musicbrainzReleaseId. This is safe because
  AcoustIdCacheEntry.musicbrainzReleaseId was already nullable (empty
  string maps to NULL in the schema from day one).

Depends on: cmrt-feature-fingerprint-clear-reanalyze (#26 )

[coveralls]

Coverage Report for CI Build 27123028384

Coverage decreased (-0.007%) to 30.459%

Details

• Coverage decreased (-0.007%) from the base build.
• Patch coverage: 34 uncovered changes across 1 file (0 of 34 lines covered, 0.0%).
• 1 coverage regression across 1 file.

Uncovered Changes

File	Changed	Covered	%
src/musicbrainz/acoustidworker.cpp	34	0	0.0%

Coverage Regressions

1 previously-covered line in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
src/musicbrainz/acoustidworker.cpp	1	0.0%

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Coverage Stats

Relevant Lines:	116171
Covered Lines:	35385
Line Coverage:	30.46%
Coverage Strength:	59292.24 hits per line

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💛 - Coveralls