fix(events): keep registration status reads nonblocking

apps/events/migrations/0017_registrationnotification.py

@@ -0,0 +1,37 @@
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("events", "0016_registration_cancellation_reason_and_more"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="RegistrationNotification",
+            fields=[
+                ("id", models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name="ID")),
+                ("kind", models.CharField(choices=[("confirmed", "Confirmed"), ("cancelled", "Cancelled")], max_length=10)),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                ("delivered_at", models.DateTimeField(blank=True, null=True)),
+                ("lease_until", models.DateTimeField(blank=True, null=True)),
+                (
+                    "registration",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="notification_outbox",
+                        to="events.registration",
+                    ),
+                ),
+            ],
+            options={
+                "constraints": [
+                    models.UniqueConstraint(
+                        fields=("registration", "kind"),
+                        name="unique_registration_notification",
+                    ),
+                ],
+            },
+        ),
+    ]

apps/events/migrations/0018_registrationnotification_reg_notif_pending_idx.py

@@ -0,0 +1,17 @@
+# Generated by Django 5.2.5 on 2026-10-01 09:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('events', '0017_registrationnotification'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='registrationnotification',
+            index=models.Index(condition=models.Q(('delivered_at__isnull', True)), fields=['lease_until', 'created_at'], name='reg_notif_pending_idx'),
+        ),
+    ]