Allow to hide cancellation fee from end-user in approval flow (#2735)

Co-authored-by: Richard Schreiber <wiffbi@gmail.com>

src/pretix/base/settings.py

@@ -1514,6 +1514,15 @@ DEFAULTS = {
                     "before the order is canceled and a refund is issued."),
         )
     },
+    'cancel_allow_user_paid_require_approval_fee_unknown': {
+        'default': 'False',
+        'type': bool,
+        'form_class': forms.BooleanField,
+        'serializer_class': serializers.BooleanField,
+        'form_kwargs': dict(
+            label=_("Do not show the cancellation fee to users when they request cancellation."),
+        )
+    },
     'cancel_allow_user_paid_refund_as_giftcard': {
         'default': 'off',
         'type': str,