Add OS Lyrics extension (#2656)

* draft commit

* time to fight pipeline

* round 2 changes

* remove unnecessary line

* fight taglib. again

* make taglib work again???

* add id3 tags

* taglib 1.12 vs 1.13

* use int instead for windows

* store as json now

* add migration, more tests

* support repeated line, multiline

* fix ms and support .m, .mm, .mmm

* address some concerns, make cpp a bit safer

* separate responses from model

* remove [:]

* Add trace log

* Try to unblock pipeline

* Fix merge errors

* Fix SIGSEGV error (proper handling of empty frames)

* Add fallback artist/title to structured lyrics

* Rename conflicting named vars

* Fix tests

* Do we still need ffmpeg in the pipeline?

* Revert "Do we still need ffmpeg in the pipeline?"

Yes we do.

This reverts commit 87df7f6df79bccee83f48c4b7a8118a7636a5e66.

* Does this passes now, with a newer ffmpeg version?

* Revert "Does this passes now, with a newer ffmpeg version?"

No, it does not :(

This reverts commit 372eb4b0ae05d9ffe98078e9bc4e56a9b2921f32.

* My OCD made me do it :P

---------

Co-authored-by: Deluan Quintão <deluan@navidrome.org>

server/subsonic/helpers.go

@@ -323,3 +323,45 @@ func buildAlbumID3(ctx context.Context, album model.Album) responses.AlbumID3 {
 	dir.OriginalReleaseDate = toItemDate(album.OriginalDate)
 	return dir
 }
+
+func buildStructuredLyric(mf *model.MediaFile, lyrics model.Lyrics) responses.StructuredLyric {
+	lines := make([]responses.Line, len(lyrics.Line))
+
+	for i, line := range lyrics.Line {
+		lines[i] = responses.Line{
+			Start: line.Start,
+			Value: line.Value,
+		}
+	}
+
+	structured := responses.StructuredLyric{
+		DisplayArtist: lyrics.DisplayArtist,
+		DisplayTitle:  lyrics.DisplayTitle,
+		Lang:          lyrics.Lang,
+		Line:          lines,
+		Offset:        lyrics.Offset,
+		Synced:        lyrics.Synced,
+	}
+
+	if structured.DisplayArtist == "" {
+		structured.DisplayArtist = mf.Artist
+	}
+	if structured.DisplayTitle == "" {
+		structured.DisplayTitle = mf.Title
+	}
+
+	return structured
+}
+
+func buildLyricsList(mf *model.MediaFile, lyricsList model.LyricList) *responses.LyricsList {
+	lyricList := make(responses.StructuredLyrics, len(lyricsList))
+
+	for i, lyrics := range lyricsList {
+		lyricList[i] = buildStructuredLyric(mf, lyrics)
+	}
+
+	res := &responses.LyricsList{
+		StructuredLyrics: lyricList,
+	}
+	return res
+}