Add one or more songs to a private playlist. Send a data array of song resource identifiers, each with an id and type: "songs".

If any submitted song is already assigned to the playlist, the request returns 400 and does not add duplicates.

{
  "data": [
    { "id": "12584", "type": "songs" },
    { "id": "12622", "type": "songs" }
  ]
}