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/orders.py

@@ -2,10 +2,11 @@ import copy
 import json
 import os
 import string
-from datetime import datetime
+from datetime import datetime, time
 from decimal import Decimal
 from typing import List, Union
 
+import pytz
 from django.conf import settings
 from django.db import models
 from django.db.models import F, Sum
@@ -16,12 +17,14 @@ from django.utils.encoding import escape_uri_path
 from django.utils.functional import cached_property
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
-from django.utils.timezone import now
-from django.utils.translation import ugettext_lazy as _
+from django.utils.timezone import make_aware, now
+from django.utils.translation import pgettext_lazy, ugettext_lazy as _
+
+from pretix.base.reldate import RelativeDateWrapper
 
 from ..decimal import round_decimal
 from .base import LoggedModel
-from .event import Event
+from .event import Event, SubEvent
 from .items import Item, ItemVariation, Question, QuestionOption, Quota
 
 
@@ -267,7 +270,16 @@ class Order(LoggedModel):
         """
         if self.status not in (Order.STATUS_PENDING, Order.STATUS_PAID, Order.STATUS_EXPIRED):
             return False
-        modify_deadline = self.event.settings.get('last_order_modification_date', as_type=datetime)
+
+        modify_deadline = self.event.settings.get('last_order_modification_date', as_type=RelativeDateWrapper)
+        if self.event.has_subevents and modify_deadline:
+            modify_deadline = min([
+                modify_deadline.datetime(se)
+                for se in self.event.subevents.filter(id__in=self.positions.values_list('subevent', flat=True))
+            ])
+        elif modify_deadline:
+            modify_deadline = modify_deadline.datetime(self.event)
+
         if modify_deadline is not None and now() > modify_deadline:
             return False
         if self.event.settings.get('invoice_address_asked', as_type=bool):
@@ -292,6 +304,37 @@ class Order(LoggedModel):
             and not self.event.settings.get('payment_term_expire_automatically')
         )
 
+    @property
+    def ticket_download_date(self):
+        dl_date = self.event.settings.get('ticket_download_date', as_type=RelativeDateWrapper)
+        if dl_date:
+            if self.event.has_subevents:
+                dl_date = min([
+                    dl_date.datetime(se)
+                    for se in self.event.subevents.filter(id__in=self.positions.values_list('subevent', flat=True))
+                ])
+            else:
+                dl_date = dl_date.datetime(self.event)
+        return dl_date
+
+    @property
+    def payment_term_last(self):
+        tz = pytz.timezone(self.event.settings.timezone)
+        term_last = self.event.settings.get('payment_term_last', as_type=RelativeDateWrapper)
+        if term_last:
+            if self.event.has_subevents:
+                term_last = min([
+                    term_last.datetime(se).date()
+                    for se in self.event.subevents.filter(id__in=self.positions.values_list('subevent', flat=True))
+                ])
+            else:
+                term_last = term_last.datetime(self.event).date()
+            term_last = make_aware(datetime.combine(
+                term_last,
+                time(hour=23, minute=59, second=59)
+            ), tz)
+        return term_last
+
     def _can_be_paid(self) -> Union[bool, str]:
         error_messages = {
             'late_lastdate': _("The payment can not be accepted as the last date of payments configured in the "
@@ -299,9 +342,9 @@ class Order(LoggedModel):
             'late': _("The payment can not be accepted as it the order is expired and you configured that no late "
                       "payments should be accepted in the payment settings."),
         }
-
-        if self.event.settings.get('payment_term_last'):
-            if now() > self.event.payment_term_last:
+        term_last = self.payment_term_last
+        if term_last:
+            if now() > term_last:
                 return error_messages['late_lastdate']
 
         if self.status == self.STATUS_PENDING:
@@ -320,9 +363,11 @@ class Order(LoggedModel):
         quota_cache = {}
         try:
             for i, op in enumerate(positions):
-                quotas = list(op.item.quotas.all()) if op.variation is None else list(op.variation.quotas.all())
+                quotas = list(op.quotas)
                 if len(quotas) == 0:
-                    raise Quota.QuotaExceededException(error_messages['unavailable'])
+                    raise Quota.QuotaExceededException(error_messages['unavailable'].format(
+                        item=str(op.item) + (' - ' + str(op.variation) if op.variation else '')
+                    ))
 
                 for quota in quotas:
                     if quota.id not in quota_cache:
@@ -430,6 +475,8 @@ class AbstractPosition(models.Model):
     """
     A position can either be one line of an order or an item placed in a cart.
 
+    :param subevent: The date in the event series, if event series are enabled
+    :type subevent: SubEvent
     :param item: The selected item
     :type item: Item
     :param variation: The selected ItemVariation or null, if the item has no variations
@@ -449,6 +496,12 @@ class AbstractPosition(models.Model):
     :param meta_info: Additional meta information on the position, JSON-encoded.
     :type meta_info: str
     """
+    subevent = models.ForeignKey(
+        SubEvent,
+        null=True, blank=True,
+        on_delete=models.CASCADE,
+        verbose_name=pgettext_lazy("subevent", "Date"),
+    )
     item = models.ForeignKey(
         Item,
         verbose_name=_("Item"),
@@ -520,6 +573,12 @@ class AbstractPosition(models.Model):
     def net_price(self):
         return self.price - self.tax_value
 
+    @property
+    def quotas(self):
+        return (self.item.quotas.filter(subevent=self.subevent)
+                if self.variation is None
+                else self.variation.quotas.filter(subevent=self.subevent))
+
 
 class OrderPosition(AbstractPosition):
     """