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/forms/__init__.py

@@ -7,6 +7,7 @@ from django.utils.crypto import get_random_string
 from hierarkey.forms import HierarkeyForm
 
 from pretix.base.models import Event
+from pretix.base.reldate import RelativeDateField, RelativeDateTimeField
 
 from .validators import PlaceholderValidator  # NOQA
 
@@ -56,6 +57,9 @@ class SettingsForm(i18nfield.forms.I18nFormMixin, HierarkeyForm):
         kwargs['locales'] = self.locales
         kwargs['initial'] = self.obj.settings.freeze()
         super().__init__(*args, **kwargs)
+        for f in self.fields.values():
+            if isinstance(f, (RelativeDateTimeField, RelativeDateField)):
+                f.set_event(self.obj)
 
     def get_new_filename(self, name: str) -> str:
         nonce = get_random_string(length=8)