Add sub-events and relative date settings (#503)

* Data model

* little crud

* SubEventItemForm etc

* Drop SubEventItem.active, quota editor

* Fix failing tests

* First frontend stuff

* Addons form stuff

* Quota calculation

* net price display on EventIndex

* Add tests, solve some bugs

* Correct quota selection in more places, consolidate pricing logic

* Fix failing quota tests

* Fix TypeError

* Add tests for checkout

* Fixed a bug in QuotaForm

* Prevent immutable cart if a quota was removed from an item

* Add tests for pricing

* Handle waiting list

* Filter in check-in list

* Fixed import lost in rebase

* Fix waiting list widget

* Voucher management

* Voucher redemption

* Fix broken tests

* Add subevents to OrderChangeManager

* Create a subevent during event creation

* Fix bulk voucher creation

* Introduce subevent.active

* Copy from for subevents

* Show active in list

* ICal download for subevents

* Check start and end of presale

* Failing tests / show cart logic

* Test

* Rebase migrations

* REST API integration of sub-events

* Integrate quota calculation into the traditional quota form

* Make subevent argument to add_position optional

* Log-display foo

* pretixdroid and subevents

* Filter by subevent

* Add more tests

* Some mor tests

* Rebase fixes

* More tests

* Relative dates

* Restrict selection in relative datetime widgets

* Filter subevent list

* Re-label has_subevents

* Rebase fixes, subevents in calendar view

* Performance and caching issues

* Refactor calendar templates

* Permission tests

* Calendar fixes and month selection

* subevent selection

* Rename subevents to dates

* Add tests for calendar views

src/pretix/presale/views/__init__.py

@@ -30,7 +30,7 @@ class CartMixin:
             cartpos = queryset.order_by(
                 'item', 'variation'
             ).select_related(
-                'item', 'variation', 'addon_to'
+                'item', 'variation', 'addon_to', 'subevent', 'subevent__event', 'subevent__event__organizer'
             ).prefetch_related(
                 *prefetch
             )
@@ -73,11 +73,14 @@ class CartMixin:
             )
             addon_penalty = 1 if pos.addon_to else 0
             if downloads or pos.pk in has_addons or pos.addon_to:
-                return i, addon_penalty, pos.pk, 0, 0, 0, 0,
+                return i, addon_penalty, pos.pk, 0, 0, 0, 0, (pos.subevent_id or 0)
             if answers and (has_attendee_data or pos.item.questions.all()):
-                return i, addon_penalty, pos.pk, 0, 0, 0, 0,
+                return i, addon_penalty, pos.pk, 0, 0, 0, 0, (pos.subevent_id or 0)
 
-            return 0, addon_penalty, 0, pos.item_id, pos.variation_id, pos.price, (pos.voucher_id or 0)
+            return (
+                0, addon_penalty, 0, pos.item_id, pos.variation_id, pos.price, (pos.voucher_id or 0),
+                (pos.subevent_id or 0)
+            )
 
         positions = []
         for k, g in groupby(sorted(lcp, key=keyfunc), key=keyfunc):
@@ -144,7 +147,7 @@ def get_cart(request):
         ).order_by(
             'item', 'variation'
         ).select_related(
-            'item', 'variation'
+            'item', 'variation', 'subevent', 'subevent__event', 'subevent__event__organizer'
         ).prefetch_related(
             'item__questions', 'answers'
         )