Expose product mapping in event_copy_data signal

src/pretix/base/models/event.py

@@ -431,7 +431,10 @@ class Event(EventMixin, LoggedModel):
             else:
                 s.save()
 
-        event_copy_data.send(sender=self, other=other)
+        event_copy_data.send(
+            sender=self, other=other,
+            tax_map=tax_map, category_map=category_map, item_map=item_map, variation_map=variation_map,
+        )
 
     def get_payment_providers(self) -> dict:
         """

src/pretix/base/signals.py

@@ -223,7 +223,10 @@ You don't need to copy data inside the general settings storage which is cloned
 but you might need to modify that data.
 
 The ``sender`` keyword argument will contain the event of the **new** event. The ``other``
-keyword argument will contain the event to **copy from**.
+keyword argument will contain the event to **copy from**. The keyword arguments
+``tax_map``, ``category_map``, ``item_map``, and ``variation_map`` contain mappings
+from object IDs in the original event to objects in the new event of the respective
+types.
 """
 
 periodic_task = django.dispatch.Signal()