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/models/vouchers.py

@@ -5,11 +5,11 @@ from django.core.exceptions import ValidationError
 from django.db import models
 from django.utils.crypto import get_random_string
 from django.utils.timezone import now
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import pgettext_lazy, ugettext_lazy as _
 
 from ..decimal import round_decimal
 from .base import LoggedModel
-from .event import Event
+from .event import Event, SubEvent
 from .items import Item, ItemVariation, Quota
 
 
@@ -33,6 +33,8 @@ class Voucher(LoggedModel):
 
     :param event: The event this voucher is valid for
     :type event: Event
+    :param subevent: The date in the event series, if event series are enabled
+    :type subevent: SubEvent
     :param code: The secret voucher code
     :type code: str
     :param max_usages: The number of times this voucher can be redeemed
@@ -80,6 +82,12 @@ class Voucher(LoggedModel):
         related_name="vouchers",
         verbose_name=_("Event"),
     )
+    subevent = models.ForeignKey(
+        SubEvent,
+        null=True, blank=True,
+        on_delete=models.CASCADE,
+        verbose_name=pgettext_lazy("subevent", "Date"),
+    )
     code = models.CharField(
         verbose_name=_("Voucher code"),
         max_length=255, default=generate_code,
@@ -186,6 +194,8 @@ class Voucher(LoggedModel):
                                         'Otherwise it might be unclear which quotas to block.'))
         else:
             raise ValidationError(_('You need to specify either a quota or a product.'))
+        if self.event.has_subevents and self.block_quota and not self.subevent:
+            raise ValidationError(_('If you want this voucher to block quota, you need to select a specific date.'))
 
     def save(self, *args, **kwargs):
         self.code = self.code.upper()