feat:(server): support reading lyrics from filesystem (#2897)

* simplified lyrics handling

* address initial feedback

* add some trace and error logging

* allow fallback lyrics

* update nit

* restore artist/title filter only

core/lyrics/lyrics.go

@@ -0,0 +1,37 @@
+package lyrics
+
+import (
+	"context"
+	"strings"
+
+	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/model"
+)
+
+func GetLyrics(ctx context.Context, mf *model.MediaFile) (model.LyricList, error) {
+	var lyricsList model.LyricList
+	var err error
+
+	for pattern := range strings.SplitSeq(strings.ToLower(conf.Server.LyricsPriority), ",") {
+		pattern = strings.TrimSpace(pattern)
+		switch {
+		case pattern == "embedded":
+			lyricsList, err = fromEmbedded(ctx, mf)
+		case strings.HasPrefix(pattern, "."):
+			lyricsList, err = fromExternalFile(ctx, mf, pattern)
+		default:
+			log.Error(ctx, "Invalid lyric pattern", "pattern", pattern)
+		}
+
+		if err != nil {
+			log.Error(ctx, "error parsing lyrics", "source", pattern, err)
+		}
+
+		if len(lyricsList) > 0 {
+			return lyricsList, nil
+		}
+	}
+
+	return nil, nil
+}