[keycloak-user] Hardcoded Group IdP mapper

Hello, I have a use case for which I need to add users created during the broker login flow to a group depending on their IdP. So similar to the Hardcoded Role mapper but with a group. I know this is possible with a custom mapper which is what I will fall back on but, to save myself some trouble, can anyone think of another way to do it? I know there is a script authenticator but there isn't a lot of documentation about it so not sure if I can add it there somehow?