code: public static String getAbsoluteUrl(SlingHttpServletRequest request, String url) {
          if (!isExternalUrl(url) && url.startsWith("/")) {
              String scheme = request.getScheme().toLowerCase();
              url = scheme + "://" + getAuthority(request) + url;
          }
          return url;
      }
docs: Makes a URL already built external; the url should be built by the 'getUrl' method.
  
  @param request the request as the externalization context
  @param url     the url value (the local URL)
  @return