*
     * @param username the username for authentication
     * @param password the password for authentication
     * @return an optional containing the authenticated user if successful, empty otherwise
     */
    public OptionalEntity<FessUser> login(final String username, final String password) {
        // Add defensive null/blank checks

                    log.debug("No digest setup " + anonymous + " B " + isSignatureSetupRequired());
                }
                setSessionSetup(response);

                // Initialize multi-channel after successful session setup
                initializeMultiChannel();

                // Initialize witness support for fast failover
                initializeWitnessSupport();

                if (ex != null) {

            final IAuthenticationResult result = app.acquireTokenSilently(parameters).get(acquisitionTimeout, TimeUnit.MILLISECONDS);
            if (logger.isDebugEnabled()) {
                logger.debug("Silent token acquisition successful");
            }
            return result;
        } catch (final Exception e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Silent token acquisition failed: {}", e.getMessage());