Adds Lyrics Support to Subsonic API (#1379)

* Add function 'isSynced' that identifies if lyrics are synced or not and add tests for the same

* implement 'getLyrics' which returns lyrics if they exist

Signed-off-by: Dheeraj Lalwani <lalwanidheeraj1234@gmail.com>

* remove timestamps frorom the the lyrics if they are synced, fix filters & clean up code

Signed-off-by: Dheeraj Lalwani <lalwanidheeraj1234@gmail.com>

* add snapshot tests for the 'Lyrics' response & add some clean up

Signed-off-by: Dheeraj Lalwani <lalwanidheeraj1234@gmail.com>

* add tests for 'GetLyrics' function

Signed-off-by: Dheeraj Lalwani <lalwanidheeraj1234@gmail.com>

* update the snapshot test & the test for 'GetLyrics' function

Signed-off-by: Dheeraj Lalwani <lalwanidheeraj1234@gmail.com>

server/subsonic/api.go

@@ -146,6 +146,7 @@ func (api *Router) routes() http.Handler {
 		withThrottle := r.With(middleware.ThrottleBacklog(maxRequests, consts.RequestThrottleBacklogLimit, consts.RequestThrottleBacklogTimeout))
 		h(withThrottle, "getAvatar", c.GetAvatar)
 		h(withThrottle, "getCoverArt", c.GetCoverArt)
+		h(withThrottle, "getLyrics", c.GetLyrics)
 	})
 	r.Group(func(r chi.Router) {
 		c := initStreamController(api)
@@ -155,7 +156,6 @@ func (api *Router) routes() http.Handler {
 	})
 
 	// Not Implemented (yet?)
-	h501(r, "getLyrics")
 	h501(r, "jukeboxControl")
 	h501(r, "getAlbumInfo", "getAlbumInfo2")
 	h501(r, "getShares", "createShare", "updateShare", "deleteShare")