ember-cli-mirage factory only includes one child - ember.js

Question

I have my mirage setup with two models and factories like so
mirage/models/user.js
import { Model, hasMany } from 'ember-cli-mirage';
export default Model.extend({
posts: hasMany()
});
mirage/models/post.js
import { Model, belongsTo } from 'ember-cli-mirage';
export default Model.extend({
user: belongsTo()
});
mirage/factory/user.js
import { Factory, faker } from 'ember-cli-mirage';
export default Factory.extend({
name(i) {
return `Person ${i}`;
},
afterCreate(user, server){
server.create('post', 10, { user });
}
});
mirage/factories/post.js
import { Factory, association } from 'ember-cli-mirage';
export default Factory.extend({
title(i) {
return `Show ${i}`;
},
description(){
return faker.lorem.paragraph();
},
user: association()
});
mirage/serializers/user.js
import { RestSerializer } from 'ember-cli-mirage';
export default RestSerializer.extend({
include: ['posts']
});
mirage/scenarios/default.js
export default function(server) {
server.createList('user', 10);
}
In my model hook I make a request to this.get('store').findAll('user') and then I loop over it in my template. The problem I have is that this get request only includes 1 post per user. What I would have expected is to get 10 posts created per user.
What am I missing here?