docs: public static String resolve(final String baseUrl, final String relUrl) {
          URL base;
          try {
              try {
                  base = new URL(baseUrl);
              } catch (MalformedURLException e) {
                  // the base is unsuitable, but the attribute/rel may be abs on its own, so try that
                  URL abs = new URL(relUrl);
                  return abs.toExternalForm();
              }
              return resolve(base, relUrl).toExternalForm();
          } catch (MalformedURLException e) {
              return "";
          }
      }