* connect without authentication.
 *
 * ```java
 * for (Challenge challenge : response.challenges()) {
 *   // If this is preemptive auth, use a preemptive credential.
 *   if (challenge.scheme().equalsIgnoreCase("OkHttp-Preemptive")) {
 *     return response.request().newBuilder()
 *         .header("Proxy-Authorization", "secret")
 *         .build();
 *   }
 * }
 * return null; // Didn't find a preemptive auth scheme.

      if (responseCode != 200 || contentType == null) {
        return;
      }

      MediaType mediaType = MediaType.parse(contentType);
      if (mediaType == null || !mediaType.subtype().equalsIgnoreCase("html")) {
        return;
      }

      Document document = Jsoup.parse(response.body().string(), url.toString());
      for (Element element : document.select("a[href]")) {