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/base/payment.py

@@ -1,5 +1,5 @@
+import logging
 from collections import OrderedDict
-from datetime import date
 from decimal import Decimal
 from typing import Any, Dict, Union
 
@@ -16,11 +16,14 @@ from i18nfield.forms import I18nFormField, I18nTextarea
 from i18nfield.strings import LazyI18nString
 
 from pretix.base.decimal import round_decimal
-from pretix.base.models import Event, Order, Quota
+from pretix.base.models import CartPosition, Event, Order, Quota
+from pretix.base.reldate import RelativeDateField, RelativeDateWrapper
 from pretix.base.settings import SettingsSandbox
 from pretix.base.signals import register_payment_providers
 from pretix.presale.views import get_cart_total
 
+logger = logging.getLogger(__name__)
+
 
 class PaymentProviderForm(Form):
     def clean(self):
@@ -150,11 +153,10 @@ class BasePaymentProvider:
                  required=False
              )),
             ('_availability_date',
-             forms.DateField(
+             RelativeDateField(
                  label=_('Available until'),
                  help_text=_('Users will not be able to choose this payment provider after the given date.'),
                  required=False,
-                 widget=forms.DateInput(attrs={'class': 'datepickerfield'})
              )),
             ('_fee_reverse_calc',
              forms.BooleanField(
@@ -230,12 +232,36 @@ class BasePaymentProvider:
 
         return form
 
-    def _is_still_available(self, now_dt=None):
+    def _is_still_available(self, now_dt=None, cart_id=None, order=None):
         now_dt = now_dt or now()
         tz = pytz.timezone(self.event.settings.timezone)
-        availability_date = self.settings.get('_availability_date', as_type=date)
+
+        availability_date = self.settings.get('_availability_date', as_type=RelativeDateWrapper)
         if availability_date:
+            if self.event.has_subevents and cart_id:
+                availability_date = min([
+                    availability_date.datetime(se).date()
+                    for se in self.event.subevents.filter(
+                        id__in=CartPosition.objects.filter(
+                            cart_id=cart_id, event=self.event
+                        ).values_list('subevent', flat=True)
+                    )
+                ])
+            elif self.event.has_subevents and order:
+                availability_date = min([
+                    availability_date.datetime(se).date()
+                    for se in self.event.subevents.filter(
+                        id__in=order.positions.values_list('subevent', flat=True)
+                    )
+                ])
+            elif self.event.has_subevents:
+                logger.error('Payment provider is not subevent-ready.')
+                return False
+            else:
+                availability_date = availability_date.datetime(self.event).date()
+
             return availability_date >= now_dt.astimezone(tz).date()
+
         return True
 
     def is_allowed(self, request: HttpRequest) -> bool:
@@ -247,7 +273,7 @@ class BasePaymentProvider:
 
         The default implementation checks for the _availability_date setting to be either unset or in the future.
         """
-        return self._is_still_available()
+        return self._is_still_available(cart_id=request.session.session_key)
 
     def payment_form_render(self, request: HttpRequest) -> str:
         """
@@ -385,7 +411,7 @@ class BasePaymentProvider:
 
         :param order: The order object
         """
-        return self._is_still_available()
+        return self._is_still_available(order=order)
 
     def order_can_retry(self, order: Order) -> bool:
         """