Add support for SAML

[brianehlert]

In the world of OIDC, SAML is still a thing and it is actually part of OAuth2.

NGINX Plus recently introduced a SAML implementation, following its very popular OIDC reference implementation.
https://github.com/nginxinc/nginx-saml/

Walkthrough with Entra ID here:
https://www.nginx.com/blog/configure-nginx-plus-for-saml-sso-with-microsoft-entra-id/

A SAML Policy would need to be developed following saml_sp_configuration.conf
The Policy and related configuration would need to be enabled
This would need to be able to co-exist along side OIDC, JWT and other Policies
Ability to apply at the server and/or location block (different unique Policies per location block is possible)
SAML key/value would need to be synchronized across the pods