Closes #5858: Implement a quick-add UI widget for related objects (#18016)

* WIP

* Misc cleanup

* Add warning re: nested quick-adds

netbox/tenancy/forms/forms.py

@@ -25,6 +25,7 @@ class TenancyForm(forms.Form):
         label=_('Tenant'),
         queryset=Tenant.objects.all(),
         required=False,
+        quick_add=True,
         query_params={
             'group_id': '$tenant_group'
         }