message: add to queue endpoint
diff: @@ -1781,6 +1781,24 @@ impl Spotify {
  }
  }
  + ///[Add an item to the end fo the user's current playback queue](https://developer.spotify.com/console/post-queue/)
  + /// Add and item to the end of the user's playback queue
  + /// Parameters:
  + /// - uri - THe uri of the item to add, Track or Episode
  + /// - device id - The id of the device targeting
  + /// - If no device ID provided the user's currently active device is targeted
  + pub async fn add_item_to_queue(
  + &self,
  + item: String,
  + device_id: Option<String>,
  + ) -> Result<CUDResult, failure::Error> {
  + let mut params = Map::new();
  + params.insert("uri".to_owned(), item.into());
  + let url = self.append_device_id("me/player/queue", device_id);
  + let res = self.post(&url, &Value::Object(params)).await?;
  + self.convert_result::<CUDResult>(&res)
  + }
  +
  pub fn convert_result<'a, T: Deserialize<'a>>(
  &self,
  input: &'a str,
  