title: Rails_admin with devise
body: <p>I have Rails_admin installed with devise and I want to restrict the /admin dashboard to only admins. For the moment my code looks like :</p>
  
  <pre><code>config.authenticate_with do
      warden.authenticate! scope: :user
    end
  
  config.current_user_method(&amp;:current_user)
  </code></pre>
  
  <p>As you can see users can get in to the dashboard so I want only the users with a boolean true in the admin column of the user table to get access to the dashboard.</p>
  
  <p>How would you suggest I do this ? </p>