New Twiddle

application.serializer.js

import DS from "ember-data";

export default DS.JSONAPISerializer.extend({
  serialize(snapshot, options) {
    let json = this._super(...arguments)
    console.log(json)
    return json;
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  init(){
    this._super(...arguments)
    this.store.createRecord('modela', {name: 'hi'}).save()
  }
});

models.modela.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  name: attr('string'),
  
  modelbs: hasMany('modelb'),
  modelcs: hasMany('modelc')
});

models.modelb.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  name: attr('string'),
  
  modelas: hasMany('modela')
});

models.modelc.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
    name: attr('string'),
  	modela: belongsTo('modela')
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"    
  },
  "addons": {
    "github.com:velrest/data.git"
  }
}