List campaigns

{
  "success": true,
  "data": [
    {
      "id": "string",
      "name": "string",
      "audience_id": "string",
      "status": "pending",
      "total_count": 0,
      "sent_count": 0,
      "delivered_count": 0,
      "read_count": 0,
      "failed_count": 0,
      "from": "string",
      "created_at": "2019-08-24T14:15:22Z",
      "started_at": "2019-08-24T14:15:22Z",
      "completed_at": "2019-08-24T14:15:22Z",
      "aborted_at": "2019-08-24T14:15:22Z"
    }
  ],
  "limit": 0,
  "skip": 0,
  "total": 0
}

{
  "success": false,
  "error": {
    "code": "string",
    "message": "string",
    "request_id": "string",
    "details": [
      {
        "path": "string",
        "code": "string",
        "message": "string"
      }
    ]
  }
}