title: Rails 4 and Devise: add custom var at current_user
body: <p>How can i customize <code>current_user</code> adding an attribute like <code>current_user.array</code> ? <br></p>
  
  <p>EDIT: better explaination <br>
  I need to save the records ids of an associated table cause i dont wanna call the db every time a user visit a page like <code>products/1</code> to control if the product is associated at the <code>current_user</code>. With the ids i can do something like <code>if the array stored in session[:ids] contain params[:id] current_user can access to the page else redirect_to root_path</code> </p>