Add migration to force slash after hostname in returnurl prefixes (#3948)

* Add migration to force slash after hostname in returnurl prefixes

* isort

* add dependency to pretixbase

src/pretix/plugins/returnurl/migrations/0001_initial.py

@@ -0,0 +1,12 @@
+# Generated by Django 4.2.10 on 2024-03-01 13:55
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+    ]
+
+    operations = [
+    ]

src/pretix/plugins/returnurl/migrations/0002_auto_20240301_1355.py

@@ -0,0 +1,39 @@
+# Generated by Django 4.2.10 on 2024-03-01 13:55
+import re
+
+from django.core.cache import cache
+from django.db import migrations
+
+MISSING_SLASH = re.compile(r"^https?://[^/]*$")
+
+
+def force_slash_after_hostname(prefix):
+    prefix = prefix.strip()
+    if MISSING_SLASH.match(prefix):
+        return prefix + "/"
+    else:
+        return prefix
+
+
+def update_returnurl_prefixes(app, schema_editor):
+    EventSettingsStore = app.get_model('pretixbase', 'Event_SettingsStore')
+
+    for setting in EventSettingsStore.objects.filter(key='returnurl_prefix'):
+        prefixes = setting.value.split("\n")
+        new_prefixes = [force_slash_after_hostname(prefix) for prefix in prefixes]
+        new_value = "\n".join(new_prefixes)
+        setting.value = new_value
+        cache.delete('hierarkey_{}_{}'.format('event', setting.object_id))
+        setting.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('returnurl', '0001_initial'),
+        ('pretixbase', '0257_item_default_price_not_null'),
+    ]
+
+    operations = [
+        migrations.RunPython(update_returnurl_prefixes, migrations.RunPython.noop)
+    ]