This commit allows the Transport Actions for the SSO realms to
indicate the realm that should be used to authenticate the
constructed AuthenticationToken. This is useful in the case that
many authentication realms of the same type have been configured
and where the caller of the API(Kibana or a custom web app) already
know which realm should be used so there is no need to iterate all
the realms of the same type.
The realm parameter is added in the relevant REST APIs as optional
so as not to introduce any breaking change.
This commit adds a configuration guide for the newly introduced
OpenID Connect realm. The guide is similar to the style of the
SAML Guide and shares certain parts where applicable (role mapping)
It also contains a short section on how the realm can be used for
authenticating users without Kibana.
Co-Authored-By: Lisa Cawley <lcawley@elastic.co>
Backport of #41423 and #42555