serializer.js

{
  "data": {
    "id": 1,
    "type": "user",
    "attributes": {
      "first" : payload.general.first,
      "last" : payload.general.last,
    },
    relationships: {
      userRealty: {
        data: {
          id: '1',
          "type": "user-realty",
          "relationships" : {
            userRealtyLicenses: {
              id: '1',
              "type" : "user-realty-license"
            }
          }
        }
      }
    }
  },
  included: [{
    id: '1',
    type: 'user-realty',
    "attributes": {
      mlsName: payload.realty.mls_name,
      mlsUserId: payload.realty.mls_user_id,
      licenseNum: payload.realty.license_num
    }
  },
  {
    id:'1',
    type: 'user-realty-license',
    "attributes": {
      "type":"license",
      "state" : "georgia"
    }
  },
  {
    id:'2',
    type: 'user-realty-license',
    "attributes": {
      "type":"license",
      "state" : "alabama"
    }
  }]
}