New implementation of sales channels (#4111)

Co-authored-by: Martin Gross <gross@rami.io>

src/tests/plugins/ticketoutputpdf/test_api.py

@@ -43,7 +43,7 @@ def env():
     t.limit_events.add(event)
     item1 = Item.objects.create(event=event, name="Ticket", default_price=23)
     tl = event.ticket_layouts.create(name="Foo", default=True, layout='[{"a": 2}]')
-    TicketLayoutItem.objects.create(layout=tl, item=item1)
+    TicketLayoutItem.objects.create(layout=tl, item=item1, sales_channel=o.sales_channels.get(identifier="web"))
     return event, tl, item1