The htaccess-register function allows you to create your own authentication methods. Like Apache you can create external authentication modules and plug them into the .htaccess module via htaccess-register. Two sample modules are provided in server_root/plugins/nsapi/htaccess.
You can use external modules to create one or more new directives. For example, you might specify the user database for authentication. The directives may not appear within <Limit> or <LimitExcept> tags.