core: simplify group serializer for user API endpoint (#3899)

* core/api: Adding simple group serializer to improve user retrieval performance

Due to the exhaustive use of the user_obj the performance suffers
greatly if the users are assigned to large groups. This simple fix adds
a new serializer that does not expose the user_obj within a group.

* core/api: Update schema

Update to the schema based on the new SimpleGroupSerializer

* core/api: Fix black and pylint

* make naming consistent, remove unnecessary fields

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>
Co-authored-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/core/api/users.py

@@ -46,7 +46,6 @@ from structlog.stdlib import get_logger
 
 from authentik.admin.api.metrics import CoordinateSerializer
 from authentik.api.decorators import permission_required
-from authentik.core.api.groups import GroupSerializer
 from authentik.core.api.used_by import UsedByMixin
 from authentik.core.api.utils import LinkSerializer, PassiveSerializer, is_dict
 from authentik.core.middleware import (
@@ -74,6 +73,26 @@ from authentik.tenants.models import Tenant
 LOGGER = get_logger()
 
 
+class UserGroupSerializer(ModelSerializer):
+    """Simplified Group Serializer for user's groups"""
+
+    attributes = JSONField(required=False)
+    parent_name = CharField(source="parent.name", read_only=True)
+
+    class Meta:
+
+        model = Group
+        fields = [
+            "pk",
+            "num_pk",
+            "name",
+            "is_superuser",
+            "parent",
+            "parent_name",
+            "attributes",
+        ]
+
+
 class UserSerializer(ModelSerializer):
     """User Serializer"""
 
@@ -83,7 +102,7 @@ class UserSerializer(ModelSerializer):
     groups = PrimaryKeyRelatedField(
         allow_empty=True, many=True, source="ak_groups", queryset=Group.objects.all()
     )
-    groups_obj = ListSerializer(child=GroupSerializer(), read_only=True, source="ak_groups")
+    groups_obj = ListSerializer(child=UserGroupSerializer(), read_only=True, source="ak_groups")
     uid = CharField(read_only=True)
     username = CharField(max_length=150)