Features: 1) Add sku field to multiple serializers and GraphQL object types for better product identification;

Fixes: 1) Remove unnecessary `IntegrityError` import in 0038_backfill_product_sku migration;

Extra: 1) Minor formatting cleanup in migration files.

core/graphene/object_types.py

@@ -507,6 +507,7 @@ class ProductType(DjangoObjectType):
         interfaces = (relay.Node,)
         fields = (
             "uuid",
+            "sku",
             "category",
             "brand",
             "tags",

core/migrations/0038_backfill_product_sku.py

@@ -1,4 +1,4 @@
-from django.db import migrations, transaction, IntegrityError
+from django.db import migrations, transaction
 
 
 def generate_unique_sku(Product, make_candidate, taken):

core/migrations/0039_alter_product_sku.py

@@ -5,7 +5,6 @@ from django.db import migrations, models
 
 
 class Migration(migrations.Migration):
-
     dependencies = [
         ("core", "0038_backfill_product_sku"),
     ]

core/serializers/detail.py

@@ -326,6 +326,7 @@ class ProductDetailSerializer(ModelSerializer):
         model = Product
         fields = [
             "uuid",
+            "sku",
             "name",
             "description",
             "partnumber",

core/serializers/simple.py

@@ -163,6 +163,7 @@ class ProductSimpleSerializer(ModelSerializer):
         fields = [
             "uuid",
             "name",
+            "sku",
             "is_digital",
             "slug",
             "description",