I think I’ve got this working now, but am not sure if it’s a typo in the docs though, or maybe I just confused it with a different section…
https://theforeman.org/manuals/3.4/index.html#5.7.5Populateusersandattributes
REMOTE_USER_GROUP
but the SSO config for Foreman is expecting REMOTE_USER_GROUPS
from the claim
After updating Apache config, all is right in the world, and we have properly assigned users automatically created tied to External groups
<Location /users/extlogin>
Require valid-user
AuthType openid-connect
LogLevel debug
RequestHeader set REMOTE_USER %{OIDC-preferred_username}e
RequestHeader set REMOTE_USER_EMAIL %{OIDC-email}e
RequestHeader set REMOTE_USER_FIRSTNAME %{OIDC-given_name}e
RequestHeader set REMOTE_USER_LASTNAME %{OIDC-family_name}e
RequestHeader set REMOTE_USER_GROUPS %{OIDC-groups}e
</Location>