auth.js

App.Auth = Ember.Auth.create({
  // ...
  modules: ["emberModel"]
});

ember-model-auth.js

Ember.Auth.Module.EmberModel = Ember.Object.extend({
  init: function() {
    this.patch();
  },

  patch: function() {
    var self = this;
    if (Ember.RESTAdapter) {
      Ember.RESTAdapter.reopen({
        _ajax: function(url, params, method) {
          var settings = {
            url: url,
            type: method,
            dataType: "json",
            data: params
          };

          return self.auth._request.send(settings);
        }
      });
    }
  }
});