title: How to define url X-AMZ-Expires in Shrine configuration
body: <p>When we call the method <code>url</code> the value for <code>X-AMZ-Expires</code> can be defined with the argument <code>expires_in</code>. </p>
  
  <p>Is there a way to define this on Shrine's configuration file or in the uploader so that every time I call <code>url</code> I wouldn't need to give the value of <code>expired_in</code>?</p>