Force price t obe decimal when creating purchased items for events

aleksis/apps/paweljong/models.py

 from datetime import datetime
+from decimal import Decimal
 
 from django.contrib.contenttypes.models import ContentType
 from django.db import models
@@ -310,7 +311,7 @@ class EventRegistration(ExtensibleModel):
         yield PurchasedItem(
             name=self.event.display_name,
             quantity=1,
-            price=self.event.cost,
+            price=Decimal(self.event.cost),
             currency="EUR",
             sku="",
             tax_rate=7,