docs: public URLNormalizer addDomainTrailingSlash() {
          String urlRoot = HttpURL.getRoot(url);
          String path = toURL().getPath();
          if (StringUtils.isNotBlank(path)) {
              // there is a path so do nothing
              return this;
          }
          String urlRootAndPath = urlRoot + "/";
          url = StringUtils.replaceOnce(url, urlRoot, urlRootAndPath);
          return this;
      }