feat(dbus): Add dphys-swapfile configuration functionality

Implemented `configure_dphys_swapfile` to manage the dphys-swapfile
service, including automatic swapfile removal when the service is
disabled. Updated feature registry to support dphys-swapfile
configuration.

src/revpi_middleware/dbus_middleware1/system_config/interface_config.py

@@ -5,7 +5,13 @@
 from collections import namedtuple
 from logging import getLogger
 
-from .revpi_config import ConfigActions, configure_avahi_daemon, configure_gui, simple_systemd
+from .revpi_config import (
+    ConfigActions,
+    configure_avahi_daemon,
+    configure_dphys_swapfile,
+    configure_gui,
+    simple_systemd,
+)
 from ..dbus_helper import DbusInterface
 
 log = getLogger(__name__)
@@ -73,7 +79,7 @@ def get_feature(feature: str) -> FeatureFunction:
 AVAILABLE_FEATURES = {
     "gui": FeatureFunction(configure_gui, []),
     "revpi-con-can": False,
-    "dphys-swapfile": False,
+    "dphys-swapfile": FeatureFunction(configure_dphys_swapfile, []),
     "pimodbus-master": FeatureFunction(simple_systemd, ["pimodbus-master.service"]),
     "pimodbus-slave": FeatureFunction(simple_systemd, ["pimodbus-slave.service"]),
     "systemd-timesyncd": FeatureFunction(simple_systemd, ["systemd-timesyncd.service"]),

src/revpi_middleware/dbus_middleware1/system_config/revpi_config.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # SPDX-FileCopyrightText: 2025 KUNBUS GmbH
 # SPDX-License-Identifier: GPL-2.0-or-later
+import subprocess
 from enum import Enum, IntEnum
 from logging import getLogger
 from os import X_OK, access
@@ -105,6 +106,21 @@ def configure_avahi_daemon(action: ConfigActions):
     return return_value
 
 
+def configure_dphys_swapfile(action: ConfigActions):
+    return_value = simple_systemd(action, "dphys-swapfile.service")
+
+    # Post actions for dphys-swapfile
+    if action is ConfigActions.DISABLE:
+        # Remove swapfile afer disabling the service unit
+        subprocess.call(
+            ["/sbin/dphys-swapfile", "uninstall"],
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
+
+    return return_value
+
+
 def configure_gui(action: ConfigActions):
     gui_available = access("/usr/bin/startx", X_OK)