Add new attechment functionality to new models

- Giving the ol' refactor tractor a fresh coat of paint

InvenTree/stock/api.py

@@ -29,6 +29,7 @@ from .serializers import StockItemAttachmentSerializer
 
 from InvenTree.views import TreeSerializer
 from InvenTree.helpers import str2bool, isNull
+from InvenTree.api import AttachmentMixin
 
 from decimal import Decimal, InvalidOperation
 
@@ -645,7 +646,7 @@ class StockList(generics.ListCreateAPIView):
     ]
 
 
-class StockAttachmentList(generics.ListCreateAPIView):
+class StockAttachmentList(generics.ListCreateAPIView, AttachmentMixin):
     """
     API endpoint for listing (and creating) a StockItemAttachment (file upload)
     """
@@ -653,22 +654,10 @@ class StockAttachmentList(generics.ListCreateAPIView):
     queryset = StockItemAttachment.objects.all()
     serializer_class = StockItemAttachmentSerializer
 
-    filter_backends = [
-        DjangoFilterBackend,
-        filters.OrderingFilter,
-        filters.SearchFilter,
-    ]
-
     filter_fields = [
         'stock_item',
     ]
 
-    def perform_create(self, serializer):
-
-        attachment = serializer.save()
-        attachment.user = self.request.user
-        attachment.save()
-
 
 class StockTrackingList(generics.ListCreateAPIView):
     """ API endpoint for list view of StockItemTracking objects.