Add playlists to a playlist group

POST https://api.7digital.com/1.2/user/playlists/groups/5891c01057abd1052cc2bf1b?userId=12345&country=GB&oauth_consumer_key=YOUR_KEY_HERE&oauth_token=...

{
  "playlistGroup": {
    "id": "5891c01057abd1052cc2bf1b",
    "name": "My Mix A",
    "playlistCount": 3,
    "lastUpdated": "2017-02-01T11:01:36.283Z",
    "_links": {
      "self": {
        "href": "http://api.7digital.com/1.2/user/playlists/groups/5891c01057abd1052cc2bf1b"
      }
    },
    "playlists": [
      {
        "id": "557ff48c17cd7e1698668d49",
        "name": "test sonos",
        "_links": {
          "self": {
            "href": "http://api.7digital.com/1.2/playlists/557ff48c17cd7e1698668d49"
          },
          "details": {
            "href": "http://api.7digital.com/1.2/playlists/557ff48c17cd7e1698668d49/details"
          },
          "tracks": {
            "href": "http://api.7digital.com/1.2/playlists/557ff48c17cd7e1698668d49/tracks"
          }
        },
        "trackCount": 10,
        "tags": [

        ],
        "status": "Published",
        "visibility": "Private",
        "annotations": {

        },
        "image": "http://artwork-cdn.7static.com/static/img/sleeveart/00/022/004/0002200406_$size$.jpg",
        "lastUpdated": "2015-06-16T10:04:09.314Z"
      },
      {
        "id": "5891c01057abd1052cc2bf1b"
      }
    ]
  }
}