fix(scanner): preserve parentheses in lyrics when processing alias tags (#4985)

Signed-off-by: Deluan <deluan@navidrome.org>

model/metadata/metadata.go

@@ -250,7 +250,15 @@ func processPairMapping(name model.TagName, mapping model.TagConf, lowered model
 	id3Base := parseID3Pairs(name, lowered)
 
 	if len(aliasValues) > 0 {
-		id3Base = append(id3Base, parseVorbisPairs(aliasValues)...)
+		// For lyrics, don't use parseVorbisPairs as parentheses in lyrics content
+		// should not be interpreted as language keys (e.g. "(intro)" is not a language)
+		if name == model.TagLyrics {
+			for _, v := range aliasValues {
+				id3Base = append(id3Base, NewPair("xxx", v))
+			}
+		} else {
+			id3Base = append(id3Base, parseVorbisPairs(aliasValues)...)
+		}
 	}
 	return id3Base
 }

model/metadata/metadata_test.go

@@ -246,6 +246,18 @@ var _ = Describe("Metadata", func() {
 					metadata.NewPair("eng", "Lyrics"),
 				))
 			})
+
+			It("should preserve lyrics starting with parentheses from alias tags", func() {
+				props.Tags = model.RawTags{
+					"LYRICS": {"(line one)\nline two\nline three"},
+				}
+				md = metadata.New(filePath, props)
+
+				Expect(md.All()).To(HaveKey(model.TagLyrics))
+				Expect(md.Strings(model.TagLyrics)).To(ContainElements(
+					metadata.NewPair("xxx", "(line one)\nline two\nline three"),
+				))
+			})
 		})
 
 		Describe("ReplayGain", func() {