Closes #21016: Add missing MPTT tree indexes (#21432)

Upgrade django-mptt to 0.18.0 and add empty indexes tuple to MPTT model
Meta classes. The empty tuple triggers Django's migration detection for
indexes that django-mptt adds dynamically (see
django-mptt/django-mptt#682). We cannot define the indexes explicitly
because the MPTT fields don't exist when the Meta class is evaluated.

Affected models: Region, SiteGroup, Location, DeviceRole, Platform,
ModuleBay, InventoryItem, InventoryItemTemplate, TenantGroup,
ContactGroup, WirelessLANGroup

netbox/tenancy/migrations/0023_add_mptt_tree_indexes.py

@@ -0,0 +1,23 @@
+# Generated by Django 5.2.10 on 2026-02-13 13:36
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('extras', '0134_owner'),
+        ('tenancy', '0022_add_comments_to_organizationalmodel'),
+        ('users', '0015_owner'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='contactgroup',
+            index=models.Index(fields=['tree_id', 'lft'], name='tenancy_contactgroup_tree_d2ce'),
+        ),
+        migrations.AddIndex(
+            model_name='tenantgroup',
+            index=models.Index(fields=['tree_id', 'lft'], name='tenancy_tenantgroup_tree_ifebc'),
+        ),
+    ]

netbox/tenancy/models/contacts.py

@@ -22,6 +22,9 @@ class ContactGroup(NestedGroupModel):
     """
     class Meta:
         ordering = ['name']
+        # Empty tuple triggers Django migration detection for MPTT indexes
+        # (see #21016, django-mptt/django-mptt#682)
+        indexes = ()
         constraints = (
             models.UniqueConstraint(
                 fields=('parent', 'name'),

netbox/tenancy/models/tenants.py

@@ -29,6 +29,9 @@ class TenantGroup(NestedGroupModel):
 
     class Meta:
         ordering = ['name']
+        # Empty tuple triggers Django migration detection for MPTT indexes
+        # (see #21016, django-mptt/django-mptt#682)
+        indexes = ()
         verbose_name = _('tenant group')
         verbose_name_plural = _('tenant groups')