def add_user_tracks_to_playlist(user_id, playlist_id, uris = [], position = nil)
      params = { uris: Array.wrap(uris)[0..99].join(',') }
      if position
        params.merge!(position: position)
      end
      run(:post, "/v1/users/#{user_id}/playlists/#{playlist_id}/tracks", [201], JSON.dump(params), false)
    end
def add_user_tracks_to_playlist(user_id, playlist_id, uris = [], position = nil)
      params = { uris: Array.wrap(uris)[0..99].join(',') }
      if position
        params.merge!(position: position)
      end
      run(:post, "/v1/users/#{user_id}/playlists/#{playlist_id}/tracks", [201], JSON.dump(params), false)
    end
Add an Array of track uris to an existing playlist.

 Adding tracks to a user's public playlist requires authorization of the playlist-modify-public scope;
 adding tracks to a private playlist requires the playlist-modify-private scope.

 client.add_user_tracks_to_playlist('1181346016', '7i3thJWDtmX04dJhFwYb0x', %w(spotify:track:4iV5W9uYEdYUVa79Axb7Rh spotify:track:2lzEz3A3XIFyhMDqzMdcss))