[Request]: Add general OIDC SSO documentation

[sebastianbuechler]

Summary

In the docs we can find a lot of SSO provider examples including Keycloak SSO via OIDC. Since Strapi uses passport.js for SSO it probably uses this strategy for the Keycloak implementation. However, I can't find any details about a general OIDC integration with other providers.

Why is it needed?

It's not clear if the Keycloak SSO via OIDC is the general OIDC integration and will work with other providers via OIDC (and how).

Suggested solution(s)

Add documentation for a general OIDC integration.

Related issue(s)/PR(s)

No response