Marionette.js with Rails (Devise) Authentication

<%= f.label :email %>
<br />
<%= f.text_field :email %>

<%= f.label :username %>
<br />
<%= f.text_field :username %>

devise :token_authenticatable

before_save :ensure_authentication_token

# You can skip storage for :http_auth and :token_auth by adding those symbols to the array below.
config.skip_session_storage = [:token_auth]

# Defines name of the authentication token params key
config.token_authentication_key = :auth_token

devise_for :users, :controllers => { :registrations => 'registrations', :sessions => 'sessions' }

class SessionsController < Devise::SessionsController
  def create
    respond_to do |format|
      format.html {
        super
      }
      format.json {
        build_resource
        user = User.find_for_database_authentication(:email => params[:user][:email])
        return invalid_login_attempt unless resource

        if user.valid_password?(params[:user][:password])
          render :json => { :auth_token => user.authentication_token }, success: true, status: :created
        else
          invalid_login_attempt
        end
      }
    end
  end

  def destroy
    respond_to do |format|
      format.html {
        super
      }
      format.json {
        user = User.find_by_authentication_token(params[:auth_token])
        if user
          user.reset_authentication_token!
          render :json => { :message => 'Session deleted.' }, :success => true, :status => 204
        else
          render :json => { :message => 'Invalid token.' }, :status => 404
        end
      }
    end
  end

  protected
  def invalid_login_attempt
    warden.custom_failure!
    render json: { success: false, message: 'Error with your login or password' }, status: 401
  end
end