message: add recorder_track_in_playlist()
diff: @@ -550,7 +550,34 @@ impl Spotify {
  Err(e) => Err(e),
  }
  }
  -
  + ///https://developer.spotify.com/web-api/reorder-playlists-tracks/
  + ///Reorder tracks in a playlist
  + ///Parameters:
  + ///- user_id - the id of the user
  + ///- playlist_id - the id of the playlist
  + ///- range_start - the position of the first track to be reordered
  + ///- range_length - optional the number of tracks to be reordered (default: 1)
  + ///- insert_before - the position where the tracks should be inserted
  + ///- snapshot_id - optional playlist's snapshot ID
  + pub fn recorder_tracks_in_playlist(&self,
  + user_id: &str,
  + playlist_id: &mut str,
  + range_start: i32,
  + range_length: i32,
  + insert_before: i32,
  + snapshot_id: Option<String>)
  + -> Option<CUDResult> {
  + let plid = self.get_id(Type::Playlist, playlist_id);
  + let payload = json!({
  + "range_start": range_start,
  + "range_length": range_length,
  + "insert_before": insert_before,
  + "snapshot_id": snapshot_id
  + });
  + let mut url = String::from(format!("users/{}/playlists/{}/tracks",user_id,plid));
  + let result = self.put(&mut url, payload);
  + self.convert_result::<CUDResult>(&result.unwrap_or_default())
  + }
  fn convert_result<'a, T: Deserialize<'a>>(&self, input: &'a str) -> Option<T> {
  match serde_json::from_str::<T>(input) {
  