Draft: Use keycloak as another source

[nikzen]

Description

It would be great if we can also sync userdata from keycloak. It can follow the same logic as the other sources. You can find the keycloak API description here: https://www.keycloak.org/docs-api/latest/rest-api/index.html#_users

Solution

GET /admin/realms/{realm}/users will list all users. It is possible to filter users based on query parameters. We can therefor build different search queries to implement import or deactivation of users.