code: public static String getRequestProtocol(){
          String protocol = header("X-Forwarded-Proto");
          return Util.blank(protocol)? protocol(): protocol;
      }
docs: This method returns a protocol of a request to web server if this container is fronted by one, such that
  it sets a header <code>X-Forwarded-Proto</code> on the request and forwards it to the Java container.
  If such header is not present, than the {@link #protocol()} method is used.
  
  @return protocol of web server request if <code>X-Forwarded-Proto</code> header is found, otherwise current
  protocol.