Allow to print question answers on invoices

src/pretix/base/models/items.py

@@ -1034,6 +1034,10 @@ class Question(LoggedModel):
         help_text=_('This question will only show up in the backend.'),
         default=False
     )
+    print_on_invoice = models.BooleanField(
+        verbose_name=_('Print answer on invoices'),
+        default=False
+    )
     dependency_question = models.ForeignKey(
         'Question', null=True, blank=True, on_delete=models.SET_NULL, related_name='dependent_questions'
     )