Add "bulk" argument to order_placed signal (#5505)

* datasync: add immediate parameter to enqueue_order

* interactive argument for order_placed signal

The ``interactive`` argument specifies whether the order was
placed interactively, by a customer (as opposed to via a bulk
import or the REST API).

* use bulk=True instead of interactive=False to mark bulk imports

src/pretix/base/services/modelimport.py

@@ -221,7 +221,7 @@ def import_orders(event: Event, fileid: str, settings: dict, locale: str, user,
 
             for o in orders:
                 with language(o.locale, event.settings.region):
-                    order_placed.send(event, order=o)
+                    order_placed.send(event, order=o, bulk=True)
                     if o.status == Order.STATUS_PAID:
                         order_paid.send(event, order=o)