Allow payment providers to define custom form fields / templates

src/pretix/plugins/banktransfer/payment.py

@@ -1,4 +1,6 @@
 from collections import OrderedDict
+from django.template import Context
+from django.template.loader import get_template
 from django.utils.translation import ugettext_lazy as _
 from django import forms
 
@@ -16,3 +18,8 @@ class BankTransfer(BasePaymentProvider):
              required=False
          ))
     ])
+
+    def checkout_form_render(self, request) -> str:
+        template = get_template('pretixplugins/banktransfer/checkout_payment_form.html')
+        ctx = Context({'request': request, 'event': self.event, 'settings': self.settings})
+        return template.render(ctx)

src/pretix/plugins/banktransfer/templates/pretixplugins/banktransfer/checkout_payment_form.html

@@ -0,0 +1,10 @@
+{% load i18n %}
+
+<p>{% blocktrans trimmed %}
+    After completing your purchase, we will ask you to transfer the money to the following
+    bank account, using a personal reference code.
+{% endblocktrans %}</p>
+
+<address>
+    {{ settings.bank_details|linebreaksbr }}
+</address>