Introduce cancellation requests (#1627)

* Allow to adjust the cancellation fee without JS

* Introduce cancellation requests

* ignore→delete

* Change a few things after Martin's review

* Add a few tests

src/pretix/base/migrations/0148_cancellationrequest.py

@@ -0,0 +1,24 @@
+# Generated by Django 3.0.4 on 2020-03-25 10:05
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0147_user_session_token'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='CancellationRequest',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False)),
+                ('created', models.DateTimeField(auto_now_add=True)),
+                ('cancellation_fee', models.DecimalField(decimal_places=2, max_digits=10)),
+                ('refund_as_giftcard', models.BooleanField(default=False)),
+                ('order', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='cancellation_requests', to='pretixbase.Order')),
+            ],
+        ),
+    ]

src/pretix/base/models/orders.py

@@ -470,6 +470,8 @@ class Order(LockModel, LoggedModel):
         """
         from .checkin import Checkin
 
+        if self.cancellation_requests.exists():
+            return False
         positions = list(
             self.positions.all().annotate(
                 has_checkin=Exists(Checkin.objects.filter(position_id=OuterRef('pk')))
@@ -2208,6 +2210,13 @@ class CachedCombinedTicket(models.Model):
     created = models.DateTimeField(auto_now_add=True)
 
 
+class CancellationRequest(models.Model):
+    order = models.ForeignKey(Order, on_delete=models.CASCADE, related_name='cancellation_requests')
+    created = models.DateTimeField(auto_now_add=True)
+    cancellation_fee = models.DecimalField(max_digits=10, decimal_places=2)
+    refund_as_giftcard = models.BooleanField(default=False)
+
+
 @receiver(post_delete, sender=CachedTicket)
 def cachedticket_delete(sender, instance, **kwargs):
     if instance.file:

src/pretix/base/services/orders.py

@@ -404,6 +404,7 @@ def _cancel_order(order, user=None, send_mail: bool=True, api_token=None, device
 
         order.log_action('pretix.event.order.canceled', user=user, auth=api_token or oauth_application or device,
                          data={'cancellation_fee': cancellation_fee})
+        order.cancellation_requests.all().delete()
 
         if send_mail:
             email_template = order.event.settings.mail_text_order_canceled

src/pretix/base/settings.py

@@ -917,6 +917,16 @@ DEFAULTS = {
             help_text=_("With this option enabled, your customers can choose to get a smaller refund to support you.")
         )
     },
+    'cancel_allow_user_paid_require_approval': {
+        'default': 'False',
+        'type': bool,
+        'form_class': forms.BooleanField,
+        'serializer_class': serializers.BooleanField,
+        'form_kwargs': dict(
+            label=_("Customers can only request a cancellation that needs to be approved by the event organizer "
+                    "before the order is canceled and a refund is issued."),
+        )
+    },
     'cancel_allow_user_paid_refund_as_giftcard': {
         'default': 'off',
         'type': str,