add nbss_id as index to Appointments

To more efficiently search for them in
`create_appointments` command

Author: Harriethw

manage_breast_screening/notifications/migrations/0015_add_nbss_id_as_index_to_appointments.py

@@ -0,0 +1,17 @@
+# Generated by Django 5.2.3 on 2025-08-26 11:17
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('notifications', '0014_remove_blob_name_from_appointments'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='appointment',
+            index=models.Index(fields=['nbss_id'], name='notificatio_nbss_id_b218dc_idx'),
+        ),
+    ]

manage_breast_screening/notifications/models.py

@@ -109,6 +109,9 @@ class Appointment(models.Model):
     The screening appointment used to build the message.
     """
 
+    class Meta:
+        indexes = [models.Index(fields=["nbss_id"])]
+
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     batch_id = models.CharField(max_length=30, default="")
     nbss_id = models.CharField(max_length=30, unique=True)