* </p>
 * <ul>
 *   <li>Starting and finishing threads</li>
 *   <li>Starting and cleaning up crawling</li>
 *   <li>Handling unsupported URLs</li>
 *   <li>Checking last modified dates</li>
 *   <li>Getting content</li>
 *   <li>Handling redirects</li>
 *   <li>Processing responses</li>
 *   <li>Handling exceptions during crawling and child URL processing</li>
 *   <li>Handling cases where no URL is in the queue</li>

    /** Indicates checking the last modified date of a resource. */
    CHECK_LAST_MODIFIED,
    /** Indicates the resource has not been modified. */
    NOT_MODIFIED,
    /** Indicates getting content from a resource. */
    GET_CONTENT,
    /** Indicates a redirect location was found. */
    REDIRECT_LOCATION,
    /** Indicates processing a response. */
    PROCESS_RESPONSE,

 * and provides access to the wrapped factory instance through getParent().
 *
 * All crawler client management operations (adding, getting clients, setting client map) are delegated
 * to the wrapped factory instance.
 *
 * This class implements the decorator pattern to extend CrawlerClientFactory functionality while
 * maintaining the same interface.
 *
 */