Reducing request time for PartList API

- Initial query time = 5.91s
- Prefetch related part categories = 3.64s

InvenTree/part/serializers.py

@@ -58,6 +58,11 @@ class PartSerializer(serializers.ModelSerializer):
     image_url = serializers.CharField(source='get_image_url', read_only=True)
     category_name = serializers.CharField(source='category_path', read_only=True)
 
+    @staticmethod
+    def setup_eager_loading(queryset):
+        queryset = queryset.prefetch_related('category')
+        return queryset
+
     class Meta:
         model = Part
         partial = True