List customer groups

{
  "data": [
    {
      "id": 0,
      "created_at": "2019-08-24T14:15:22Z",
      "updated_at": "2019-08-24T14:15:22Z",
      "customers": [
        {
          "id": 0,
          "name": "string",
          "role": "string"
        }
      ]
    }
  ],
  "total": 0
}