Self-service refund form (#1135)

* Auto-refund

* Add missing template

* Notification for requested refund

* Model-level tests

* Add front-end tests

* Default to notify

src/pretix/base/migrations/0106_auto_20190118_1527.py

@@ -0,0 +1,31 @@
+# Generated by Django 2.1.5 on 2019-01-18 15:27
+from django.db import migrations
+
+
+def enable_notifications_for_everyone(apps, schema_editor):
+    NotificationSetting = apps.get_model('pretixbase', 'NotificationSetting')
+    User = apps.get_model('pretixbase', 'User')
+    create = []
+    for u in User.objects.iterator():
+        create.append(NotificationSetting(
+            user=u,
+            action_type='pretix.event.order.refund.requested',
+            event=None,
+            method='mail',
+            enabled=True
+        ))
+        if len(create) > 200:
+            NotificationSetting.objects.bulk_create(create)
+            create.clear()
+    NotificationSetting.objects.bulk_create(create)
+    create.clear()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('pretixbase', '0105_auto_20190112_1512'),
+    ]
+
+    operations = [
+        migrations.RunPython(enable_notifications_for_everyone, migrations.RunPython.noop)
+    ]