[keycloak-user] User Federation

Hi all, I wonder if anyone could help me. I'm trying to set up a realm with user federation. I'd like that realm to point to another realm within the same instance of Keycloak. Is this possible and if so, how do I go about it? The reason for this is we have one application supporting different contracts, users have different permissions in different contracts. We think we can achieve this by setting up 1 client over multiple realms and using one set of users in all those realms but with different permissions in each realm. Any advice is much appreciated. Kind regards, James