title: How to concatenate I18n.t() strings in content_for() helper?
body: <p>I'd like to concatenate the strings from my localization file "admin.titles.index" and "%{model_name}" (which takes from activerecord.models.harddisk).</p>
  
  <p>I tried with:</p>
  
  <pre><code>&lt;% title = I18n.t("admin.titles.index") + I18n.t("%{model_name}", 
             model_name: admin.model_name, 
             pluralized_model_name: admin.model_name.pluralize)%&gt;
  
  &lt;% content_for(:title, title) %&gt;
  </code></pre>
  
  <p>But I get an error message: </p>
  
  <pre><code>translation missing: de.%{model_name}
  </code></pre>
  
  <p>How can I fix that?</p>