title: Which unsupported characters exist for the dotenv file?
body: <p>I'm trying to store a Facebook API Access-Token in Fortrabbit's environment variables. (.env and app secret)</p>
  
  <p>But I get the message:</p>
  
  <blockquote>
    <p>Unsupported characters or malformed nested ENV vars.</p>
  </blockquote>
  
  <p>I think the problem might be, that my token contains a <code>|</code> character.</p>
  
  <ul>
  <li>Is there a list of unsupported characters?</li>
  <li>Is there a way to escape this character?</li>
  </ul>
  
  <p>Thanks</p>