Add carrier field to Refund model and update Stripe views

Introduces a OneToOneField for carrier in the Refund model to support future integration and refactoring. Adds and updates TODO comments for email template usage, error handling in Stripe webhooks, and clarifies logic placement in Stripe models.

backend/account/tasks.py

@@ -10,6 +10,7 @@ from .models import CustomUser
 
 logger = get_task_logger(__name__)
 
+# TODO: předělat funkci ať funguje s base.html šablonou na emaily !!!
 def send_email_with_context(recipients, subject, message=None, template_name=None, html_template_name=None, context=None):
     """
     General function to send emails with a specific context.

backend/commerce/models.py

@@ -546,7 +546,15 @@ class Refund(models.Model):
             "return_reason": return_reason,
         }
 
-        #TODO: přesunou zásilkovna field tady taky (ostranit z order několik balíku)
+        #TODO: přesunou zásilkovna field tady taky (zkontrolovat jestli jsou views napojené a použít metodu send z carrier)
+        carrier = models.OneToOneField(
+            "Carrier",
+            on_delete=models.CASCADE,
+            related_name="refund",
+            null=True,
+            blank=True
+        )
+        
 
         html_string = render_to_string("refund/customer_in_package_returning_form.html", context)
         pdf_bytes = HTML(string=html_string).write_pdf()

backend/thirdparty/stripe/models.py

@@ -3,8 +3,6 @@ from django.apps import apps
 
 # Create your models here.
 
-#TODO: logika a interakce bude na stripu (třeba aktualizovaní objednávky na zaplacenou apod.)
-
 from .client import StripeClient
     
 class StripeModel(models.Model):

backend/thirdparty/stripe/views.py

@@ -26,12 +26,13 @@ class StripeWebhook(APIView):
         sig_header = request.META['HTTP_STRIPE_SIGNATURE']
 
         try:
-            #build stripe event
+            #build stripe event (api call)
             event = stripe.Webhook.construct_event(
                 payload, sig_header, os.getenv("STRIPE_WEBHOOK_SECRET")
             )
 
         except ValueError as e:
+            # TODO: doupravit error handling, dodělat v modelu možnost pro uložení chyby a status ERROR
             logger.error(f"Invalid payload: {e}")
             return HttpResponse(status=400)