Sending a multipart message with text cards and a button

{
  "recipient": {
    "id": "USER_ID"
  },
  "message": {
    "raw": {
      "multipart": [{
        "attachment": {
          "type": "template",
          "payload": {
          "elements": [
            {
              "title": "Check out these documents:",
              "buttons": [
                {
                  "url":"https://app.thebotplatform.com/",
                  "type":"web_url",
                  "title":"Image bot tutorial"
                }
              ]
            }
          ],
          "template_type":"generic"
        }
      }
      }]
    }
  }
}