autoregister oidc user

Hi,

https://mariadb.com/kb/en/mariadb-maxscale-2208-mariadb-maxscale-configuration-guide/#admin_oidc_url

This documentation says it required to create the user before do the auth process via oidc.
It would be great if we have a configuration option to autoregister the user. So with this when I have a centralized user db so I don't need to create the users also in the maxscale api.

Also can be a nice option if we can define a group or role which is actually will be an admin user or just a viewer.