[auth] Add hail_identity to REST get users (#12889)

Context:
https://hail.zulipchat.com/#narrow/stream/300487-Hail-Batch-Dev/topic/adding.20service.20account.20name.20to.20users.20list/near/349228510

It's useful for our automation to include this in the REST response get
any get user call.

I don't know how testing works, if needed, could you guide me how to add
tests to cover this?

auth/auth/auth.py

@@ -513,12 +513,12 @@ async def post_create_user(request, userdata):  # pylint: disable=unused-argumen
 @auth.rest_authenticated_developers_only
 async def rest_get_users(request, userdata):  # pylint: disable=unused-argument
     db: Database = request.app['db']
-    users = await db.select_and_fetchall(
-        '''
-SELECT id, username, login_id, state, is_developer, is_service_account FROM users;
+    _query = '''
+SELECT id, username, login_id, state, is_developer, is_service_account, hail_identity
+FROM users;
 '''
-    )
-    return json_response([user async for user in users])
+    users = [x async for x in db.select_and_fetchall(_query)]
+    return json_response(users)
 
 
 @routes.get('/api/v1alpha/users/{user}')
@@ -529,7 +529,7 @@ async def rest_get_user(request, userdata):  # pylint: disable=unused-argument
 
     user = await db.select_and_fetchone(
         '''
-SELECT id, username, login_id, state, is_developer, is_service_account FROM users
+SELECT id, username, login_id, state, is_developer, is_service_account, hail_identity FROM users
 WHERE username = %s;
 ''',
         (username,),