Add or Update Roles for the users part of the group
Replace Existing Roles:
When the roles parameter is provided in the API request,
it replaces all the current roles assigned to the user with the new
set of roles specified in the request.
Partial Updates Not Supported:
If you want to retain existing roles while adding new ones,
you must include all existing roles along with the new roles in the roles parameter.
Any roles not included in the roles parameter will be removed from the user.