* 
     * @param type
     * @return instance for type, null if the type cannot be unwrapped
     */
    <T extends Credentials> T unwrap ( Class<T> type );


    /**
     * @return the domain the user account is in
     */
    String getUserDomain ();


    /**
     * @return whether these are anonymous credentials
     */
    boolean isAnonymous ();


    /**