/// <summary>
 /// Add one or more tracks to a user’s playlist.
 /// </summary>
 /// <param name="tracks"></param>
 /// <param name="token"></param>
 /// <returns></returns>
 public async Task AddTracks(List <Track> trackUris, AuthenticationToken token)
 {
     string tracksUri = CreateCommaSeperatedList(trackUris.Select(t => t.Uri).ToList());
     var    json      = await HttpHelper.Post("https://api.spotify.com/v1/users/" + this.Owner.Id + "/playlists/" + this.Id + "/tracks?uris=" + tracksUri, token);
 }
 /// <summary>
 /// Add a track to a user’s playlist.
 /// </summary>
 /// <param name="userId"></param>
 /// <param name="token"></param>
 /// <returns></returns>
 public async Task AddTrack(Track track, AuthenticationToken token)
 {
     await HttpHelper.Post("https://api.spotify.com/v1/users/" + this.Owner.Id + "/playlists/" + this.Id + "/tracks?uris=" + track.Uri, token);
 }