Use number field instead of transaction_id for invoic

aleksis/apps/paweljong/models.py

@@ -287,7 +287,7 @@ class EventRegistration(ExtensibleModel):
         invoice, __ = Invoice.objects.get_or_create(for_content_type=ContentType.objects.get_for_model(self), for_object_id=self.pk, defaults={
             "group": group,
             "variant": "sepa" if self.accept_sepa else "transfer",
-            "transaction_id": f"HNF-{self.date_registered.strftime('%Y-%m')}-{self.id}",
+            "number": f"HNF-{self.date_registered.strftime('%Y-%m')}-{self.id}",
             "currency": "EUR",
             "total": self._get_total_amount()[0],
             "tax": self._get_total_amount()[1],

aleksis/apps/paweljong/templates/paweljong/invoice_pdf.html

@@ -197,7 +197,7 @@
     </address>
     <article>
         <date id="date">{{ invoice.created.date }}</date>
-        <h1>{% trans "Invoice" %} {{ invoice.transaction_id }}</h1>
+        <h1>{% trans "Invoice" %} {{ invoice.number }}</h1>
 
         {% render_table invoice.purchased_items_table %}
         {% render_table invoice.totals_table %}