feat(virtualization): use native unique constraint for VirtualMachineType slug (#21970)

Replace the UniqueConstraint on the slug field with the native
`unique=True` parameter on SlugField in both the model definition and
migration. This resolves a compatibility issue with netbox_branching,
which does not handle a SlugField combined with a separate
UniqueConstraint on the same field.

netbox/virtualization/migrations/0054_virtualmachinetype.py

@@ -30,7 +30,7 @@ class Migration(migrations.Migration):
                 ('description', models.CharField(blank=True, max_length=200)),
                 ('comments', models.TextField(blank=True)),
                 ('name', models.CharField(max_length=100)),
-                ('slug', models.SlugField(max_length=100)),
+                ('slug', models.SlugField(max_length=100, unique=True)),
                 (
                     'default_vcpus',
                     models.DecimalField(
@@ -95,12 +95,4 @@ class Migration(migrations.Migration):
                 violation_error_message='Virtual machine type name must be unique.',
             ),
         ),
-        migrations.AddConstraint(
-            model_name='virtualmachinetype',
-            constraint=models.UniqueConstraint(
-                fields=('slug',),
-                name='virtualization_virtualmachinetype_unique_slug',
-                violation_error_message='Virtual machine type slug must be unique.',
-            ),
-        ),
     ]

netbox/virtualization/models/virtualmachines.py

@@ -43,6 +43,7 @@ class VirtualMachineType(ImageAttachmentsMixin, PrimaryModel):
     slug = models.SlugField(
         verbose_name=_('slug'),
         max_length=100,
+        unique=True,
     )
     default_platform = models.ForeignKey(
         to='dcim.Platform',
@@ -86,11 +87,6 @@ class VirtualMachineType(ImageAttachmentsMixin, PrimaryModel):
                 name='%(app_label)s_%(class)s_unique_name',
                 violation_error_message=_('Virtual machine type name must be unique.'),
             ),
-            models.UniqueConstraint(
-                fields=('slug',),
-                name='%(app_label)s_%(class)s_unique_slug',
-                violation_error_message=_('Virtual machine type slug must be unique.'),
-            ),
         )
         indexes = (
             models.Index(fields=('name',)),  # Default ordering