Add missing schema nullable tags (#12986)

* Synchronize detail field nullable state with model user fields

* Make me-user roles field nullable/non-required

* Make client-secret nullable

* Update api version

---------

Co-authored-by: Matthias Mair <code@mjmair.com>

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,11 +1,14 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 553
+INVENTREE_API_VERSION = 554
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 INVENTREE_API_TEXT = """
 
+v554 -> 2026-10-09 : https://github.com/inventree/InvenTree/pull/12986
+    - Add missing nullable annotations for read_only fields
+
 v553 -> 2026-10-04 : https://github.com/inventree/InvenTree/pull/12965
     - Fix user creation with 'group_ids' via the User API endpoint
 

src/backend/InvenTree/common/serializers.py

@@ -1323,6 +1323,7 @@ class OAuth2ApplicationSerializer(serializers.ModelSerializer):
             'is_builtin',
         ]
         read_only_fields = ['id', 'client_id', 'client_secret', 'is_builtin']
+        extra_kwargs = {'client_secret': {'allow_null': True}}
 
     is_builtin = serializers.SerializerMethodField()
 

src/backend/InvenTree/users/serializers.py

@@ -268,8 +268,12 @@ class ApiTokenSerializer(InvenTreeModelSerializer):
         return super().validate(data)
 
     user_detail = UserSerializer(source='user', read_only=True)
-    revoked_by_detail = UserSerializer(source='revoked_by', read_only=True)
+    revoked_by_detail = UserSerializer(
-    issued_by_detail = UserSerializer(source='issued_by', read_only=True)
+        source='revoked_by', read_only=True, allow_null=True
+    )
+    issued_by_detail = UserSerializer(
+        source='issued_by', read_only=True, allow_null=True
+    )
 
 
 class GroupSerializer(FilterableSerializerMixin, InvenTreeModelSerializer):
@@ -444,7 +448,7 @@ class MeUserSerializer(FilterableSerializerMixin, ExtendedUserSerializer):
     # they were previously served as a single '/user/me/roles/' response.
     roles = OptionalField(
         serializer_class=serializers.SerializerMethodField,
-        serializer_kwargs={'read_only': True},
+        serializer_kwargs={'allow_null': True, 'read_only': True},
         filter_name='roles',
     )