Refactor cancelling positions and orders in the data model (#1088)

- [x] Data model
- [x] display in order view in backend
- [x] review all usages of OrderPositions.objects
- [x] review all usages of order.positions
- [x] review all other model usages
- [x] review plugins
- [x] plugins backwards-compatible API?
- [x] decide on way forward for REST API
- [x] need to cancel fees
- [x] tests
- [ ] plugins
  - [ ] gdpr
  - [ ] reports
- [x] docs

src/pretix/plugins/banktransfer/tasks.py

@@ -50,9 +50,6 @@ def _handle_transaction(trans: BankTransaction, code: str, event: Event=None, or
 
     if trans.order.status == Order.STATUS_PAID and trans.order.pending_sum <= Decimal('0.00'):
         trans.state = BankTransaction.STATE_DUPLICATE
-    elif trans.order.status == Order.STATUS_REFUNDED:
-        trans.state = BankTransaction.STATE_ERROR
-        trans.message = ugettext_noop('The order has already been refunded.')
     elif trans.order.status == Order.STATUS_CANCELED:
         trans.state = BankTransaction.STATE_ERROR
         trans.message = ugettext_noop('The order has already been canceled.')

src/pretix/plugins/banktransfer/views.py

@@ -54,11 +54,6 @@ class ActionView(View):
                 'status': 'error',
                 'message': _('The order is already marked as paid.')
             })
-        elif trans.order.status == Order.STATUS_REFUNDED:
-            return JsonResponse({
-                'status': 'error',
-                'message': _('The order has already been refunded.')
-            })
         elif trans.order.status == Order.STATUS_CANCELED:
             return JsonResponse({
                 'status': 'error',
@@ -170,8 +165,8 @@ class ActionView(View):
         qs = self.order_qs().order_by('pk').annotate(inr=Concat('invoices__prefix', 'invoices__invoice_no')).filter(
             code
             | Q(email__icontains=u)
-            | Q(positions__attendee_name_cached__icontains=u)
-            | Q(positions__attendee_email__icontains=u)
+            | Q(all_positions__attendee_name_cached__icontains=u)
+            | Q(all_positions__attendee_email__icontains=u)
             | Q(invoice_address__name_cached__icontains=u)
             | Q(invoice_address__company__icontains=u)
             | Q(invoices__invoice_no=u)