title: Render partial with a specific variant from another partial
body: <p>Given the following views:</p>
  
  <pre><code>views/users/show.html.erb
  views/users/show.html+v2.erb
  </code></pre>
  
  <p>with the variant set to <code>v2</code> on the controller, how can I render the <code>show.html.erb</code> from the <code>show.html+v2.erb</code>?</p>
  
  <p>I would be expecting something similar to <code>formats</code> option available but can't find what it is. My best guess:</p>
  
  <p><em>stack overflow here (it tries to render itself):</em></p>
  
  <pre><code>&lt;%= render template: 'users/show', variant: :default %&gt;
  &lt;h1&gt; Additional stuff&lt;/h1&gt;
  </code></pre>
  
  <p><em>NOTE:</em> this is very simplified example so do not suggest to extract the templates. I am after the answer to the question - how to render a template(s) in a different variant.</p>