title: Apartment switch tenant based on logged user
body: <p>I'm trying to implement a custom elevator for <a href="https://github.com/influitive/apartment" rel="noreferrer">apartment</a> based on user login on a <a href="https://github.com/influitive/apartment#switching-tenants-per-request" rel="noreferrer">per request basis</a>. </p>
  
  <p>Basically what I'm trying to achieve is:</p>
  
  <ul>
  <li>Every time a request comes in, switch to the correct tenant</li>
  <li>If there's no logged user, the default tenant is select</li>
  </ul>
  
  <p>However, my problem is that I don't how to retrieve the current user from the request(<a href="http://www.rubydoc.info/gems/rack/Rack/Request" rel="noreferrer">Rack::Request</a>) object provided by the Generic Elevator. Any tips on how to do it or there's any other way to get the current user without the request?</p>
  
  <p>I'm using <a href="https://github.com/plataformatec/devise" rel="noreferrer">devise</a> for authentication.</p>