* extracts the user principal from successful authentication.
     *
     * @return The login credential containing the authenticated username,
     *         an ActionResponseCredential for authentication challenges,
     *         or null if no authentication information is available
     * @throws SsoLoginException if SPNEGO authentication fails
     */
    @Override
    public LoginCredential getLoginCredential() {

 *  New: `EventListener.followUpDecision()` is called each time a response is received. It notifies
    your listener if OkHttp has decided to make a follow-up request. Some common follow-ups are
    authentication challenges and redirects.

 *  New: Handy constants for `Headers.EMPTY`, `RequestBody.EMPTY`, and `ResponseBody.EMPTY`.

 *  New: OkHttp now calls `StrictMode.noteSlowCall()` when initializing TLS on Android. Use

     * Generates a Type 3 NTLM message.
     *
     * @param username the username
     * @param password the password
     * @param domain the domain
     * @param workstation the workstation
     * @param challenge the Type 2 challenge message
     * @return the Base64-encoded Type 3 message
     * @throws NTLMEngineException if an NTLM engine error occurs
     * @throws CrawlingAccessException if an error occurs during message generation
     */