app/serializers/application.js

application.js

import DS from 'ember-data';

export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
  primaryKey: 'ID',
  extractArray: function(store, type, payload) {
    var payloadTemp = {};
    payloadTemp[type.typeKey] = payload;
    return this._super(store, type, payloadTemp);
  },
  extractSingle: function(store, type, payload, id) {
    var payloadTemp = {};
    payloadTemp[type.typeKey] = [payload];
    return this._super(store, type, payloadTemp, id);
  },
  attrs: {
    items: { embedded: 'always' },
    acf: { embedded: 'always' }
  }
});