fix(events): keep registration status reads nonblocking

apps/events/models.py

@@ -1,4 +1,4 @@
-from django.db import models
+from django.db import models, transaction
 from django.conf import settings
 from django.utils import timezone
 from django.utils.text import slugify
@@ -201,39 +201,59 @@ class Registration(BaseModel):
         """Human-readable label for the current registration status."""
         return self.get_status_display()
 
+    @transaction.atomic
     def save(self, *args, **kwargs):
-            # detect create vs update
-            is_create = self._state.adding
-            old_status = None
+        is_create = self._state.adding
+        old_status = None
 
-            if not is_create and self.pk:
-                old_status = (
-                    self.__class__.objects.only("status").get(pk=self.pk).status
-                )
+        if not is_create and self.pk:
+            old_status = self.__class__.objects.only("status").get(pk=self.pk).status
 
-            # save first (so we have a pk + final values)
-            super().save(*args, **kwargs)
+        super().save(*args, **kwargs)
 
-            # 1) on create -> send confirmation if pending/confirmed (and not sent before)
-            if is_create and self.status == self.StatusChoices.CONFIRMED and not self.confirmation_notification_sent_at:
-                # lazy import to avoid circular import
-                from apps.events.tasks import send_registration_confirmation_notification
-                send_registration_confirmation_notification.delay(str(self.pk))
-                self.confirmation_notification_sent_at = timezone.now()
-                super().save(update_fields=["confirmation_notification_sent_at"])
-            # 2) status changed -> cancelled
-            if (not is_create) and (old_status != self.StatusChoices.CANCELLED) and (self.status == self.StatusChoices.CANCELLED) and (not self.cancellation_notification_sent_at):
-                from apps.events.tasks import send_registration_cancellation_notification
-                send_registration_cancellation_notification.delay(str(self.pk))
-                self.cancellation_notification_sent_at = timezone.now()
-                super().save(update_fields=["cancellation_notification_sent_at"])
+        if (
+            self.status == self.StatusChoices.CONFIRMED
+            and (is_create or old_status != self.StatusChoices.CONFIRMED)
+            and not self.confirmation_notification_sent_at
+        ):
+            RegistrationNotification.objects.get_or_create(
+                registration=self,
+                kind=RegistrationNotification.Kind.CONFIRMED,
+            )
+        if (
+            not is_create
+            and old_status != self.StatusChoices.CANCELLED
+            and self.status == self.StatusChoices.CANCELLED
+            and not self.cancellation_notification_sent_at
+        ):
+            RegistrationNotification.objects.get_or_create(
+                registration=self,
+                kind=RegistrationNotification.Kind.CANCELLED,
+            )
 
-            # 3) status changed -> confirmed (if not sent before)
-            if (not is_create) and (old_status != self.StatusChoices.CONFIRMED) and (self.status == self.StatusChoices.CONFIRMED) and (not self.confirmation_notification_sent_at):
-                from apps.events.tasks import send_registration_confirmation_notification
-                send_registration_confirmation_notification.delay(str(self.pk))
-                self.confirmation_notification_sent_at = timezone.now()
-                super().save(update_fields=["confirmation_notification_sent_at"])
+        from apps.gamification.services import sync_registration_attendance
+        sync_registration_attendance(self)
 
-            from apps.gamification.services import sync_registration_attendance
-            sync_registration_attendance(self)
+
+class RegistrationNotification(models.Model):
+    """Durable intent to notify after a registration status transition commits."""
+
+    class Kind(models.TextChoices):
+        CONFIRMED = "confirmed", "Confirmed"
+        CANCELLED = "cancelled", "Cancelled"
+
+    registration = models.ForeignKey(Registration, on_delete=models.CASCADE, related_name="notification_outbox")
+    kind = models.CharField(max_length=10, choices=Kind.choices)
+    created_at = models.DateTimeField(auto_now_add=True)
+    delivered_at = models.DateTimeField(null=True, blank=True)
+    lease_until = models.DateTimeField(null=True, blank=True)
+
+    class Meta:
+        constraints = [models.UniqueConstraint(fields=["registration", "kind"], name="unique_registration_notification")]
+        indexes = [
+            models.Index(
+                fields=["lease_until", "created_at"],
+                name="reg_notif_pending_idx",
+                condition=models.Q(delivered_at__isnull=True),
+            ),
+        ]