Asynchronously loading translations with ember-intl

I'm trying to achieve asynchronous fetching of translations. I set up the publicOnly to true as docs say:

// config/ember-intl.js
module.exports = function() {
  return {
    publicOnly: true
  }
};

Skipped the step of setting up the locales key, because translations are stored in /translations folder.

Next, I should modify beforeModel hook to asynchronously fetch the translations, and that's where docs are pretty vague:

// app/routes/application.js
export default Ember.Route.extend({
  intl: Ember.inject.service(),
  async beforeModel() {
    let translations = await fetch('/api/translations.json');
    this.get('intl').addTranslations('en-us', translations);
    this.get('intl').setLocale('en-us');
  }
});

How these lines supposed to work:

let translations = await fetch('/api/translations.json');
this.get('intl').addTranslations('en-us', translations);

In runtime I have no translations.json file anywhere in the dist folder. I've got dist/translations/en-us.json only for my one and only translation and no clue how to make it work.

Service API misses documentation of addTranslations method.

Would appreciate any help.