Updates the controller configuration file name from agent.conf to

controller.conf.

This is because on K8s, the agent's configuration is in in the
controller-n path instead of machine-n on metal/VMs. We must use a
different file name, or we overwrite the agent configuration.

src/charm.py

@@ -262,7 +262,7 @@ def _controller_config_path(self) -> str:
         the local controller ID, then use it to construct a config path.
         """
         controller_id = self._config_change_socket.get_controller_agent_id()
-        return f'/var/lib/juju/agents/controller-{controller_id}/agent.conf'
+        return f'/var/lib/juju/agents/controller-{controller_id}/controller.conf'
 
     def _request_config_reload(self):
         """Send a reload request to the config reload socket"""

tests/test_charm.py

@@ -214,7 +214,7 @@ def test_dbcluster_relation_changed_write_file(
         self.harness.update_relation_data(
             relation_id, harness.charm.app.name, {'db-bind-addresses': json.dumps(bound)})
 
-        file_path = '/var/lib/juju/agents/controller-0/agent.conf'
+        file_path = '/var/lib/juju/agents/controller-0/controller.conf'
         self.assertEqual(mock_open.call_count, 2)
 
         # First call to read out the YAML