Fix #1793 -- Remove hidden URLs from EventSettingsStore and avoid saving them (#1853)

src/pretix/base/migrations/0170_remove_hidden_urls.py

@@ -0,0 +1,20 @@
+# Generated by Django 3.0.9 on 2020-11-23 15:51
+
+from django.db import migrations
+
+
+def remove_old_settings(app, schema_editor):
+    EventSettingsStore = app.get_model('pretixbase', 'Event_SettingsStore')
+
+    EventSettingsStore.objects.filter(key__startswith='payment_', key__endswith='__hidden_url').delete()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0169_checkinlist_gates'),
+    ]
+
+    operations = [
+        migrations.RunPython(remove_old_settings, migrations.RunPython.noop)
+    ]