Closes #13428: Q-in-Q VLANs (#17822)

* Initial work on #13428 (QinQ)

* Misc cleanup; add tests for Q-in-Q fields

* Address PR feedback

netbox/virtualization/tests/test_api.py

@@ -4,6 +4,7 @@ from rest_framework import status
 from dcim.choices import InterfaceModeChoices
 from dcim.models import Site
 from extras.models import ConfigTemplate
+from ipam.choices import VLANQinQRoleChoices
 from ipam.models import VLAN, VRF
 from utilities.testing import APITestCase, APIViewTestCases, create_test_device, create_test_virtualmachine
 from virtualization.choices import *
@@ -270,6 +271,7 @@ class VMInterfaceTest(APIViewTestCases.APIViewTestCase):
             VLAN(name='VLAN 1', vid=1),
             VLAN(name='VLAN 2', vid=2),
             VLAN(name='VLAN 3', vid=3),
+            VLAN(name='SVLAN 1', vid=1001, qinq_role=VLANQinQRoleChoices.ROLE_SERVICE),
         )
         VLAN.objects.bulk_create(vlans)
 
@@ -307,6 +309,12 @@ class VMInterfaceTest(APIViewTestCases.APIViewTestCase):
                 'untagged_vlan': vlans[2].pk,
                 'vrf': vrfs[2].pk,
             },
+            {
+                'virtual_machine': virtualmachine.pk,
+                'name': 'Interface 7',
+                'mode': InterfaceModeChoices.MODE_Q_IN_Q,
+                'qinq_svlan': vlans[3].pk,
+            },
         ]
 
     def test_bulk_delete_child_interfaces(self):