docs: protected String extractEngineName(String requestUrl) {
  
      Matcher matcher = ENGINE_REQUEST_URL_PATTERN.matcher(requestUrl);
  
      if (matcher.find()) {
        return matcher.group(1);
      } else {
        // any request that does not match a specific engine and is not an /engine request
        // is mapped to the default engine
        return DEFAULT_ENGINE_NAME;
      }
    }