* This method fetches and parses the robots.txt file to extract disallow/allow rules
     * and sitemap information.
     *
     * @param url The URL to process robots.txt for
     */
    protected void processRobotsTxt(final String url) {
        if (StringUtil.isBlank(url)) {
            throw new CrawlerSystemException("HTTP URL is null or empty. Cannot process robots.txt without a valid URL.");
        }