title: Force render format for all actions
body: <p>I want to respond with json to all formats.</p>
  
  <p>I can force the render format to <code>json</code> so the action will render <code>show.json</code> despite the <code>accept</code> header:</p>
  
  <pre><code>  def show
      render formats: :json
    end
  </code></pre>
  
  <p><strong>How I can set render format for all actions of the controller?</strong></p>
  
  <p>Something like this:</p>
  
  <pre><code>class GalleriesController &lt; ApplicationController
    formats :json
  end
  </code></pre>