title: where do devise_mapping.registerable?, devise_mapping.recoverable?....come from?
body: <p>where do <code>devise_mapping.registerable?</code>, <code>devise_mapping.recoverable?</code>....come from? I mean I can't find a file where they are indicated, can find nothing about them.</p>
  
  <p>And why is there always a "-" in the if..end structures? For instance:</p>
  
  <pre><code>&lt;%- if controller_name != 'sessions' %&gt;
    &lt;%= link_to "Sign in", new_session_path(resource_name) %&gt;&lt;br /&gt;
  &lt;% end -%&gt;
  </code></pre>