feat: Add db index to License.status field

This field is used by the license REST APIs for sorting and filtering,
as well as all endpoints which contain license counts by status, which
makes it a good candidate for being indexed.

ENT-8271

license_manager/apps/subscriptions/migrations/0066_license_subscription_plan_status_idx.py

@@ -0,0 +1,17 @@
+# Generated by Django 4.2.9 on 2024-01-29 20:24
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('subscriptions', '0065_subscriptionplan_desired_num_licenses_not_editable'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='license',
+            index=models.Index(fields=['subscription_plan', 'status'], name='subscription_plan_status_idx'),
+        ),
+    ]

license_manager/apps/subscriptions/models.py

@@ -902,6 +902,11 @@ class License(TimeStampedModel):
     .. pii_types: id,email_address
     .. pii_retirement: local_api
     """
+    class Meta:
+        indexes = [
+            models.Index(fields=["subscription_plan", "status"], name="subscription_plan_status_idx"),
+        ]
+
     uuid = models.UUIDField(
         primary_key=True,
         default=uuid4,