Closes #19840 - Enable Site Filtering for Devices in Cable Bulk Import (#19923)

* feat(dcim): Add site fields to Cable bulk import form

Introduces `side_a_site` and `side_b_site` fields for the Cable bulk
import form. Limits device choices on both sides to the selected site
for improved input validation and consistency.

* feat(dcim): Enhance test data setup with multiple sites

Refactors tests to create multiple sites and assign devices accordingly.
Updates CSV data to include `side_a_site` and `side_b_site` fields for
scenarios involving multiple sites. This improves test coverage and
alignment with real-world use cases.

* docs(dcim): Update comments explaining indent for CSV import

Improved the inline comments to clarify the rationale behind allowing
devices with duplicate names on different sites during CSV bulk import.

netbox/dcim/forms/bulk_import.py

@@ -1335,6 +1335,13 @@ class MACAddressImportForm(NetBoxModelImportForm):
 
 class CableImportForm(NetBoxModelImportForm):
     # Termination A
+    side_a_site = CSVModelChoiceField(
+        label=_('Side A site'),
+        queryset=Site.objects.all(),
+        required=False,
+        to_field_name='name',
+        help_text=_('Site of parent device A (if any)'),
+    )
     side_a_device = CSVModelChoiceField(
         label=_('Side A device'),
         queryset=Device.objects.all(),
@@ -1353,6 +1360,13 @@ class CableImportForm(NetBoxModelImportForm):
     )
 
     # Termination B
+    side_b_site = CSVModelChoiceField(
+        label=_('Side B site'),
+        queryset=Site.objects.all(),
+        required=False,
+        to_field_name='name',
+        help_text=_('Site of parent device B (if any)'),
+    )
     side_b_device = CSVModelChoiceField(
         label=_('Side B device'),
         queryset=Device.objects.all(),
@@ -1400,10 +1414,29 @@ class CableImportForm(NetBoxModelImportForm):
     class Meta:
         model = Cable
         fields = [
-            'side_a_device', 'side_a_type', 'side_a_name', 'side_b_device', 'side_b_type', 'side_b_name', 'type',
-            'status', 'tenant', 'label', 'color', 'length', 'length_unit', 'description', 'comments', 'tags',
+            'side_a_site', 'side_a_device', 'side_a_type', 'side_a_name', 'side_b_site', 'side_b_device', 'side_b_type',
+            'side_b_name', 'type', 'status', 'tenant', 'label', 'color', 'length', 'length_unit', 'description',
+            'comments', 'tags',
         ]
 
+    def __init__(self, data=None, *args, **kwargs):
+        super().__init__(data, *args, **kwargs)
+
+        if data:
+            # Limit choices for side_a_device to the assigned side_a_site
+            if side_a_site := data.get('side_a_site'):
+                side_a_device_params = {f'site__{self.fields["side_a_site"].to_field_name}': side_a_site}
+                self.fields['side_a_device'].queryset = self.fields['side_a_device'].queryset.filter(
+                    **side_a_device_params
+                )
+
+            # Limit choices for side_b_device to the assigned side_b_site
+            if side_b_site := data.get('side_b_site'):
+                side_b_device_params = {f'site__{self.fields["side_b_site"].to_field_name}': side_b_site}
+                self.fields['side_b_device'].queryset = self.fields['side_b_device'].queryset.filter(
+                    **side_b_device_params
+                )
+
     def _clean_side(self, side):
         """
         Derive a Cable's A/B termination objects.

netbox/dcim/tests/test_views.py

@@ -3266,17 +3266,27 @@ class CableTestCase(
     @classmethod
     def setUpTestData(cls):
 
-        site = Site.objects.create(name='Site 1', slug='site-1')
+        sites = (
+            Site(name='Site 1', slug='site-1'),
+            Site(name='Site 2', slug='site-2'),
+        )
+        Site.objects.bulk_create(sites)
         manufacturer = Manufacturer.objects.create(name='Manufacturer 1', slug='manufacturer-1')
         devicetype = DeviceType.objects.create(model='Device Type 1', manufacturer=manufacturer)
         role = DeviceRole.objects.create(name='Device Role 1', slug='device-role-1')
         vc = VirtualChassis.objects.create(name='Virtual Chassis')
 
+        # NOTE: By design, NetBox now allows for the creation of devices with the same name if they belong to
+        # different sites.
+        # The CSV test below demonstrates that devices with identical names on different sites can be created
+        # and referenced successfully.
         devices = (
-            Device(name='Device 1', site=site, device_type=devicetype, role=role),
-            Device(name='Device 2', site=site, device_type=devicetype, role=role),
-            Device(name='Device 3', site=site, device_type=devicetype, role=role),
-            Device(name='Device 4', site=site, device_type=devicetype, role=role),
+            # Create 'Device 1' assigned to 'Site 1'
+            Device(name='Device 1', site=sites[0], device_type=devicetype, role=role),
+            Device(name='Device 2', site=sites[0], device_type=devicetype, role=role),
+            Device(name='Device 3', site=sites[0], device_type=devicetype, role=role),
+            # Create 'Device 1' assigned to 'Site 2' (allowed since the site is different)
+            Device(name='Device 1', site=sites[1], device_type=devicetype, role=role),
         )
         Device.objects.bulk_create(devices)
 
@@ -3327,13 +3337,15 @@ class CableTestCase(
             'tags': [t.pk for t in tags],
         }
 
+        # Ensure that CSV bulk import supports assigning terminations from parent devices that share
+        # the same device name, provided those devices belong to different sites.
         cls.csv_data = (
-            "side_a_device,side_a_type,side_a_name,side_b_device,side_b_type,side_b_name",
-            "Device 3,dcim.interface,Interface 1,Device 4,dcim.interface,Interface 1",
-            "Device 3,dcim.interface,Interface 2,Device 4,dcim.interface,Interface 2",
-            "Device 3,dcim.interface,Interface 3,Device 4,dcim.interface,Interface 3",
-            "Device 1,dcim.interface,Device 2 Interface,Device 4,dcim.interface,Interface 4",
-            "Device 1,dcim.interface,Device 3 Interface,Device 4,dcim.interface,Interface 5",
+            "side_a_site,side_a_device,side_a_type,side_a_name,side_b_site,side_b_device,side_b_type,side_b_name",
+            "Site 1,Device 3,dcim.interface,Interface 1,Site 2,Device 1,dcim.interface,Interface 1",
+            "Site 1,Device 3,dcim.interface,Interface 2,Site 2,Device 1,dcim.interface,Interface 2",
+            "Site 1,Device 3,dcim.interface,Interface 3,Site 2,Device 1,dcim.interface,Interface 3",
+            "Site 1,Device 1,dcim.interface,Device 2 Interface,Site 2,Device 1,dcim.interface,Interface 4",
+            "Site 1,Device 1,dcim.interface,Device 3 Interface,Site 2,Device 1,dcim.interface,Interface 5",
         )
 
         cls.csv_update_data = (