In all environments the "domain" should be "redhat"

The user_id will be the "user_id" field in the identity header portion specific to the principal type. So it's under "user" for users and "service_account" for service account.

E.g. for a user with JWT "sub" "12345" we should see:

identity.user.user_id = "12345"

and rbac/principal subjects with "redhat/12345" ID.