Adding many-to-many relationships in ember data using JSONAPI

If I have the following many-to-many relationship

// User
export default DS.Model.create({
  name: DS.attr('string'),
  authorities: DS.hasMany()
});

// Authority
export default DS.Model.create({
  name: DS.attr('string'),
  users: DS.hasMany()
});

And I add an authority to a user

user.get('authorities').pushObject(authority);

From the JSONAPI documentation it says to use a POST request to update a hasMany relationship

POST /users/XXX/relationships/authorities
{
  "data": [
    { "type": "authorities", "id": "YYY" },
  ]
}

How can I generate this request via ember-data?