feat: article as product identifier

services/billing.py

@@ -310,8 +310,10 @@ class BillingService(BaseService):
             for product in card.products:
                 product_price = 0
                 for service in product.services:
+                    p = product.product
+                    product_identifier = p.article.strip() or p.factory_article.strip() or p.name.strip()
                     service_data = ServiceBillingDocumentPdf(
-                        name=f'[{product.product.name}] - {service.service.name}',
+                        name=f'[{product_identifier}] - {service.service.name}',
                         price=service.price,
                         quantity=product.quantity
                     )