title: is there a unique identifier that i can use in rails that is not session[:session_id]?
body: <p>I am trying to track <code>kiss_metrics</code> identifier and would like to maintain the same <code>unique_identifier</code> for the user throughout their entire time they are on the site, even after call <code>reset_session</code>. </p>
  
  <p>Something like a <code>cookie_id</code> that is the same from login to logout and the entire time they are on the site?</p>