Is it possible for keycloak to filter users by custom attribute - keycloak

Question

I'm trying to create a UMS that uses the Keycloak's REST API. Some users will be users and some other managers. To differentiate them, they'll belong to different groups and they'll inherit a different set of roles.
All of the users will have a custom attribute named locale. What I'm trying to achieve on this point, is every time a manager tries to fetch the list of users using the REST API ex. {{keycloak_url}}/admin/realms/{{realm}}/users only users with the same custom attribute locale should return.
example:
Complete list of users:
USERNAME LOCALE
manager1 en
manager2 fr
user1 en
user2 en
user3 fr
manager1 requests the users list expected result:
USERNAME LOCALE
manager1 en
user1 en
user2 en
manager2 requests the users list expected result:
USERNAME LOCALE
manager2 fr
user3 fr
Any suggestions on how to achieve this using Keycloak?
Thanks in advance.

Answer 1

Unfortunately, it's not possible. Keycloak does not provide such functionality because it is out of the scope of the SSO definition.
But you are free to implement a custom endpoint with filtering users by attribute locale taken from the manager's token.
You can find code here https://github.com/keycloak/keycloak/tree/master/examples/providers/domain-extension
Documentation

Answer 2

You can obtain it with https://www.keycloak.org/docs-api/17.0/rest-api/index.html#_users_resource
putting "q" in the string, like this:
https://localhost/admin/realms/{realm}/users?q=locale:
This will return what you need.