code: public static String urlFrom( HttpServletRequest request,
                                    String... pathSegments ) {
          return urlFrom(request.getRequestURL().toString(), pathSegments);
      }
docs: Creates an absolute url using the given request's url as base and appending optional segments.
  
  @param request a {@code non-null} {@link HttpServletRequest}
  @param pathSegments an option array of segments
  @return a string representing an absolute-url