Add explanation

src/pretix/base/views/applepay.py

@@ -4,6 +4,21 @@ from pretix.base.settings import GlobalSettingsObject
 
 
 def association(request, *args, **kwargs):
+    # This is a crutch to enable event- or organizer-level overrides for the default
+    # ApplePay MerchantID domain validation/association file.
+    # We do not provide any FormFields for this on purpose!
+    #
+    # Please refer to https://github.com/pretix/pretix/pull/3611 to get updates on
+    # the upcoming and official way to temporarily override the association-file,
+    # which will make sure that there are no conflicting requests at the same time.
+    #
+    # Should you opt to manually inject a different association-file into an organizer
+    # or event settings store, we do recommend to remove the setting once you're
+    # done and the domain has been validated.
+    #
+    # If you do not need Stripe's default domain association credential and would
+    # rather serve a different default credential, you can do so through the
+    # Global Settings editor.
     if hasattr(request, 'event'):
         settings = request.event.settings
     elif hasattr(request, 'organizer'):