How to configure keycloak to get admin-rights on synapse server

[xundeenergie]

I want to administrate my matrix-synapse server. When i did not use MAS i set my user in homeserver.yaml to be an admin.
With MAS this does not work anymore.

So i found:
#2187

But i have no idea, how to set keycloak (have a working setup here with keycloak, MAS and synapse) for admin-rights...

I found also https://www.keycloak.org/docs/latest/authorization_services/#_resource_overview how to configure keycloak for ressources and scopes.

But how do i have to configure the scope urn:synapse:admin for the ressource /_synapse/admin/* and give it to users, who are in the group "matrix-admins" on keycloak?