code: static boolean isLoginUIRequest(VaadinRequest request) {
  
          String referrer = request.getHeader("referer");
          return (referrer != null) && referrer.contains(CmsWorkplaceLoginHandler.LOGIN_HANDLER);
      }
docs: Checks whether the given request was referred from the login page.<p>
  
  @param request the request
  
  @return <code>true</code> in case of login ui requests