This commit updates code to not include deactivated users in
members list in the user groups object sent in "/register"
and "GET /user_groups" response and also in the response
returned by endpoint like "GET /user_groups/{group_id}/members".
The events code is also update to handle this -
- We expect clients to update the members list on receiving
"realm_user/update" event on deactivation. But for guests
who cannot access the user, "user_group/remove_members"
event is sent to update the group members list on deactivation.
- "user_group/add_members" event is sent to all the users on
reactivating the user.