feat(dbus): Add StatusChanged DBus signal to interface configuration

Introduced the `StatusChanged` signal in `.RevpiConfig` interface to
notify changes in feature status. Emitting this signal in `Enable` and
`Disable` methods ensures real-time updates for feature state changes.
This enhances communication and monitoring within the DBus middleware.

Signed-off-by: Sven Sager <s.sager@kunbus.com>

src/revpi_middleware/dbus_middleware1/system_config/interface_config.py

@@ -5,6 +5,8 @@
 from collections import namedtuple
 from logging import getLogger
 
+from pydbus.generic import signal
+
 from .revpi_config import (
     ConfigActions,
     configure_avahi_daemon,
@@ -42,10 +44,16 @@ class InterfaceRevpiConfig(DbusInterface):
                 <arg name="available" type="b" direction="out"/>
             </method>
             <property name="available_features" type="as" access="read"/>
+            <signal name="StatusChanged">
+                <arg name="feature" type="s"/>
+                <arg name="status" type="b"/>
+            </signal>
         </interface>
     </node>
     """
 
+    StatusChanged = signal()
+
     def Disable(self, feature: str) -> None:
         """Disable the feature."""
         feature_function = get_feature(feature)