models-user.js

import DS from 'ember-data';
import Ember from 'ember';

let attr = DS.attr,
    belongsTo = DS.belongsTo,
    hasMany = DS.hasMany;

export default DS.Model.extend({
  firstName: attr(),
  lastName: attr(),
  email: attr(),
  mls: attr(),
  licenseNum: attr()
});

serializers-user.js

import DS from 'ember-data';
import Ember from 'ember';
import ApplicationSerializer from 'acorns/serializers/application';

let camelize = Ember.String.camelize;

export default ApplicationSerializer.extend({
  extractSingle: function(store, primaryType, payload, recordId) {
    let newPayload = {},
        typeKey = primaryType.typeKey;
        
      newPayload[typeKey].firstName = payload.first;
      newPayload[typeKey].lastname = payload.last;
      newPayload[typeKey].mls = payload.mls;
      newPayload[typeKey].email = payload.email;
      newPayload[typeKey].licenseNum = payload.licenseNum;
      
    return this._super(store, primaryType, newPayload, recordId);
  },
  serialize: function(record, options) {
    let serializedResponse = {
      {
        general: {
          first: record.get('firstName'),
          last: record.get('lastName')
        },
        {
          email: {
            email: record.get('email')
          }
        },
        {
          realty: {
            mls: record.get('mls'),
            license_num: record.get('licenseNum')
          }
        }
      }
    };
    
    return serializedResponse;
  }
});