public static string GetTrackUrl(this ISpotifyActivity activity)
 => $"https://open.spotify.com/track/{activity.TrackId}";
 public static TimeSpan GetRemainingDuration(this ISpotifyActivity activity)
 => activity.EndsAt - DateTimeOffset.UtcNow;
 public static TimeSpan GetDuration(this ISpotifyActivity activity)
 => activity.EndsAt - activity.StartedAt;
 public static TimeSpan GetElapsedDuration(this ISpotifyActivity activity)
 => DateTimeOffset.UtcNow - activity.StartedAt;
 public static string GetAlbumCoverUrl(this ISpotifyActivity activity)
 => activity.AlbumId != null
         ? $"https://i.scdn.co/image/{activity.AlbumId}"
         : null;