feat(demo_data): enhance data generation with get_or_create

- Replaced `create` operations with `get_or_create` to ensure idempotency during data generation.
- Avoided redundant user, product image, and post creation when duplicates exist.
- Updated user and stock handling to leverage defaults for improved clarity.
- Prevented overwriting existing blog post and product image content.

engine/core/management/commands/demo_data.py

@@ -257,8 +257,8 @@ class Command(BaseCommand):
             Attribute.objects.filter(group__name__in=group_names).delete()
             AttributeGroup.objects.filter(name__in=group_names).delete()
 
-        self.staff_user.delete()
-        self.super_user.delete()
+        User.objects.filter(email=f"staff@{DEMO_EMAIL_DOMAIN}").delete()
+        User.objects.filter(email=f"super@{DEMO_EMAIL_DOMAIN}").delete()
 
         self.stdout.write("")
         self.stdout.write(self.style.SUCCESS("=" * 50))
@@ -409,13 +409,15 @@ class Command(BaseCommand):
                     product.description_ru_ru = prod_data["description_ru"]  # ty: ignore[invalid-assignment]
                 product.save()
 
-                Stock.objects.create(
+                Stock.objects.get_or_create(
                     vendor=vendor,
                     product=product,
-                    sku=f"GS-{prod_data['partnumber']}",
-                    price=prod_data["price"],
-                    purchase_price=prod_data["purchase_price"],
-                    quantity=prod_data["quantity"],
+                    defaults={
+                        "sku": f"GS-{prod_data['partnumber']}",
+                        "price": prod_data["price"],
+                        "purchase_price": prod_data["purchase_price"],
+                        "quantity": prod_data["quantity"],
+                    },
                 )
 
                 # Add product image
@@ -475,6 +477,9 @@ class Command(BaseCommand):
     def _save_product_image(
         self, product: Product, image_path: Path, priority: int
     ) -> None:
+        if product.images.filter(priority=priority).exists():
+            return
+
         with open(image_path, "rb") as f:
             image_content = f.read()
 
@@ -513,14 +518,16 @@ class Command(BaseCommand):
 
             existing_emails.add(email)
 
-            # Create user
-            user = User(
+            user, created = User.objects.get_or_create(
                 email=email,
-                first_name=first_name,
-                last_name=last_name,
-                is_active=True,
-                is_verified=True,
+                defaults={
+                    "first_name": first_name,
+                    "last_name": last_name,
+                    "is_active": True,
+                    "is_verified": True,
+                },
             )
+            if created:
                 user.set_password(password)
                 user.save()
 
@@ -594,12 +601,14 @@ class Command(BaseCommand):
 
             address = Address.objects.filter(user=user).first()
 
-            order = Order.objects.create(
+            order, _ = Order.objects.get_or_create(
                 user=user,
                 status=status,
                 buy_time=order_date,
-                billing_address=address,
-                shipping_address=address,
+                defaults={
+                    "billing_address": address,
+                    "shipping_address": address,
+                },
             )
 
             Order.objects.filter(pk=order.pk).update(created=order_date)
@@ -620,12 +629,14 @@ class Command(BaseCommand):
                 else:
                     op_status = random.choice(["ACCEPTED", "PENDING"])
 
-                OrderProduct.objects.create(
+                OrderProduct.objects.get_or_create(
                     order=order,
                     product=product,
-                    quantity=quantity,
-                    buy_price=round(price, 2),
-                    status=op_status,
+                    defaults={
+                        "quantity": quantity,
+                        "buy_price": round(price, 2),
+                        "status": op_status,
+                    },
                 )
 
             orders.append(order)
@@ -682,9 +693,6 @@ class Command(BaseCommand):
                 tag.save()
 
         for post_data in data.get("blog_posts", []):
-            if Post.objects.filter(title=post_data["title"]).exists():
-                continue
-
             content_en = self._load_blog_content(post_data["content_file"], "en")
             content_ru = self._load_blog_content(post_data["content_file"], "ru")
 
@@ -696,13 +704,16 @@ class Command(BaseCommand):
                 )
                 continue
 
-            post = Post(
-                author=author,
+            post, created = Post.objects.get_or_create(
                 title=post_data["title"],
-                content=content_en,
-                meta_description=post_data.get("meta_description", ""),
-                is_static_page=post_data.get("is_static_page", False),
+                defaults={
+                    "author": author,
+                    "content": content_en,
+                    "meta_description": post_data.get("meta_description", ""),
+                    "is_static_page": post_data.get("is_static_page", False),
+                },
             )
+            if created:
                 if "title_ru" in post_data:
                     post.title_ru_ru = post_data["title_ru"]  # ty:ignore[unresolved-attribute]
                 if content_ru: