Fill in last missing return types in schema (#10532)

* Add background task overview return type to schema

* Implement serializer so schema generates correctly

* Bump api version

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,12 +1,16 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 405
+INVENTREE_API_VERSION = 406
 
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 INVENTREE_API_TEXT = """
 
+v406 -> 2025-10-08: https://github.com/inventree/InvenTree/pull/10532
+    - Set return type for background task overview
+    - Implement serializer for part serial number detail
+
 v405 -> 2025-10-07: https://github.com/inventree/InvenTree/pull/10530
     - Add response to generic/status endpoint
     - Fix logic for generic status model lookup to allow searching by class name string

src/backend/InvenTree/common/api.py

@@ -557,6 +557,7 @@ class BackgroundTaskOverview(APIView):
     permission_classes = [IsAuthenticatedOrReadScope, IsAdminUser]
     serializer_class = None
 
+    @extend_schema(responses={200: common.serializers.TaskOverviewSerializer})
     def get(self, request, fmt=None):
         """Return information about the current status of the background task queue."""
         import django_q.models as q_models

src/backend/InvenTree/part/api.py

@@ -46,7 +46,6 @@ from InvenTree.mixins import (
     SerializerContextMixin,
     UpdateAPI,
 )
-from InvenTree.serializers import EmptySerializer
 from stock.models import StockLocation
 
 from . import serializers as part_serializers
@@ -594,19 +593,7 @@ class PartSerialNumberDetail(RetrieveAPI):
     """API endpoint for returning extra serial number information about a particular part."""
 
     queryset = Part.objects.all()
-    serializer_class = EmptySerializer
-
-    def retrieve(self, request, *args, **kwargs):
-        """Return serial number information for the referenced Part instance."""
-        part = self.get_object()
-
-        # Calculate the "latest" serial number
-        latest_serial = part.get_latest_serial_number()
-        next_serial = part.get_next_serial_number()
-
-        data = {'latest': latest_serial, 'next': next_serial}
-
-        return Response(data)
+    serializer_class = part_serializers.PartSerialNumberSerializer
 
 
 class PartCopyBOM(CreateAPI):

src/backend/InvenTree/part/serializers.py

@@ -1548,6 +1548,21 @@ class PartPricingSerializer(InvenTree.serializers.InvenTreeModelSerializer):
             pricing.update_pricing()
 
 
+class PartSerialNumberSerializer(InvenTree.serializers.InvenTreeModelSerializer):
+    """Serializer for Part serial number information."""
+
+    class Meta:
+        """Metaclass defining serializer fields."""
+
+        model = Part
+        fields = ['latest', 'next']
+
+    latest = serializers.CharField(
+        source='get_latest_serial_number', read_only=True, allow_null=True
+    )
+    next = serializers.CharField(source='get_next_serial_number', read_only=True)
+
+
 class PartRelationSerializer(InvenTree.serializers.InvenTreeModelSerializer):
     """Serializer for a PartRelated model."""