[fix] Add group-scoped cache invalidation task for device group context change #1070

Replace the org-wide invalidate_controller_views_cache call in
DeviceGroup.save() with a new group-scoped task
invalidate_controller_views_for_group that only clears
DeviceChecksumView entries for devices belonging to that group,
avoiding unnecessary invalidation of unrelated devices and VPN caches.

Also adds assertion in test_status_update_on_group_variable_change to
verify the scoped task is enqueued with the correct group_id.

Author: mn-ram

openwisp_controller/config/tests/test_device.py

@@ -440,8 +440,8 @@ def test_status_update_on_org_variable_change(self):
         c1.templates.add(
             self._create_template(
                 name="t-with-var",
-                config={"interfaces": [{"name": "eth0", "type": "{{ ssid }}"}]},
-                default_values={"ssid": "default"},
+                config={"interfaces": [{"name": "{{ ssid }}", "type": "ethernet"}]},
+                default_values={"ssid": "eth0"},
             )
         )
         c1.set_status_applied()
@@ -468,8 +468,8 @@ def test_status_update_on_group_variable_change(self):
         c1.templates.add(
             self._create_template(
                 name="t-with-var",
-                config={"interfaces": [{"name": "eth0", "type": "{{ ssid }}"}]},
-                default_values={"ssid": "default"},
+                config={"interfaces": [{"name": "{{ ssid }}", "type": "ethernet"}]},
+                default_values={"ssid": "eth0"},
             )
         )
         c1.set_status_applied()
@@ -480,7 +480,10 @@ def test_status_update_on_group_variable_change(self):
         c2.set_status_applied()
         dg.context = {"ssid": "OrgA"}
         dg.full_clean()
-        patch_path = "openwisp_controller.config.base.device_group.invalidate_controller_views_for_group"
+        patch_path = (
+            "openwisp_controller.config.base.device_group"
+            ".invalidate_controller_views_for_group"
+        )
         with mock.patch(patch_path) as mocked_task:
             dg.save()
             mocked_task.delay.assert_called_once_with(str(dg.id))