Fixes #18245: Make DeviceRole Hierarchical (#19008)

Made DeviceRoles hierarchical, had to also change the filtersets for Device, ConfigContext and VirtualMachine to use the TreeNodeMultipleChoiceFilter.

Note: The model was changed to use NestedGroupModel, a side-effect of this is it also adds comments field, but I thought that was better then doing a one-off just for DeviceRole and having to define the fields, validators, etc.. - keeps everything DRY / consistent.

* 18981 Make Device Roles Hierarchical

* 18981 forms, serializer

* 18981 fix tests

* 18981 fix tests

* 18981 fix tests

* 18981 fix tests

* 18981 fix tests

* 18981 fix migration merge

* 18981 fix tests

* 18981 fix filtersets

* 18981 fix tests

* 18981 comments

* 18981 review changes

netbox/dcim/models/devices.py

@@ -23,7 +23,7 @@ from extras.models import ConfigContextModel, CustomField
 from extras.querysets import ConfigContextModelQuerySet
 from netbox.choices import ColorChoices
 from netbox.config import ConfigItem
-from netbox.models import OrganizationalModel, PrimaryModel
+from netbox.models import NestedGroupModel, OrganizationalModel, PrimaryModel
 from netbox.models.mixins import WeightMixin
 from netbox.models.features import ContactsMixin, ImageAttachmentsMixin
 from utilities.fields import ColorField, CounterCacheField
@@ -468,7 +468,7 @@ class ModuleType(ImageAttachmentsMixin, PrimaryModel, WeightMixin):
 # Devices
 #
 
-class DeviceRole(OrganizationalModel):
+class DeviceRole(NestedGroupModel):
     """
     Devices are organized by functional role; for example, "Core Switch" or "File Server". Each DeviceRole is assigned a
     color to be used when displaying rack elevations. The vm_role field determines whether the role is applicable to
@@ -491,6 +491,8 @@ class DeviceRole(OrganizationalModel):
         null=True
     )
 
+    clone_fields = ('parent', 'description')
+
     class Meta:
         ordering = ('name',)
         verbose_name = _('device role')