How to display attributes of belongsTo object in Ember.js template

In my (beginner) Ember app, a survey belongsTo a user; a user hasMany surveys. In my template, I would like to display a list of surveys, and the name of the user that created them. For now, I am pushing side-loaded data into the store via the application route, and it is showing up in the ember inspector->Data. The survey info is displaying correctly in the template, but the corresponding user's firstName will not appear. Help/guidance appreciated.

survey.js (model)

import DS from 'ember-data';

export default DS.Model.extend({
  user: DS.belongsTo('user', {async: true}), //tried without async as well
  title: DS.attr(),
  post: DS.attr()
});

user.js (model)

import DS from 'ember-data';

export default DS.Model.extend({
  surveys: DS.hasMany('survey', {async: true}),  
  firstName: DS.attr()
});

application.js (application route)

export default Ember.Route.extend({
  model() {
    this.store.push({
      data: [{
        id: 1,
        type: 'survey',
        attributes: {
          title: 'My First Survey',
          post: 'This is my Survey!'
        },
        relationships: {
          user: 1
        }
      }, {
        id: 2,
        type: 'survey',
        attributes: {
          title: 'My Second Survey',
          post: 'This is survey 2!'
        },
        relationships: {
          user: 1
        }
      }, {
        id: 1,
        type: 'user',
        attributes: {
          firstName: 'Tyler'
        },
        relationships: {
          surveys: [1, 2]
        }
      }]
    });
  }
});

surveys.js (route)

export default Ember.Route.extend({
  model () {
    return this.store.findAll('survey');
  }
});

surveys.hbs (template)

<ul>
  {{#each model as |survey|}}
    <li>
      <strong>{{survey.title}}</strong> //This works
      <br>
      {{survey.post}}                   //This works
      <br>
      Author: {{survey.user.firstName}} //This does not work
    </li>
  {{/each}}
</ul>