Restore single project ID filtering for AssetAdmin

This relied on the permissions added by the default admin list filter interface. That changed from a single value to multiple, breaking the links we had on the item admin page.

concordia/admin/__init__.py

@@ -349,6 +349,12 @@ def get_queryset(self, request):
         qs = super().get_queryset(request)
         return qs.select_related("item").order_by("item__item_id", "sequence")
 
+    def lookup_allowed(self, key, value):
+        if key in ("item__project__id__exact"):
+            return True
+        else:
+            return super().lookup_allowed(key, value)
+
     def item_id(self, obj):
         return obj.item.item_id