feat(dbus): Add initial D-Bus middleware implementation

Introduce a D-Bus middleware module for revpi_middleware, including an
interface definition and a `BusProvider` class to handle D-Bus
communication. This forms the foundation for middleware interactions
using D-Bus.

src/revpi_middleware/dbus_middleware1/__init__.py

@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+# SPDX-FileCopyrightText: 2025 KUNBUS GmbH
+# SPDX-License-Identifier: GPL-2.0-or-later
+"""D-Bus middleware version 1 of revpi_middleware."""
+from ..__about__ import __author__, __copyright__, __license__, __version__
+
+REVPI_DBUS_NAME = "com.revolutionpi.middleware1"
+REVPI_DBUS_BASE_PATH = "/com/revolutionpi/middleware1"

src/revpi_middleware/dbus_middleware1/bus_provider.py

@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+# SPDX-FileCopyrightText: 2025 KUNBUS GmbH
+# SPDX-License-Identifier: GPL-2.0-or-later
+"""D-Bus bus provider for revpi_middleware."""
+from logging import getLogger
+from threading import Thread
+
+from gi.repository import GLib
+from pydbus import SystemBus
+
+from . import REVPI_DBUS_NAME
+from .process_image import InterfacePiControl
+
+log = getLogger(__name__)
+
+
+class BusProvider(Thread):
+
+    def __init__(self):
+        log.debug("enter BusProvider.__init__")
+        super().__init__()
+
+        self._bus = SystemBus()
+        self._loop = GLib.MainLoop()
+
+    def run(self):
+        log.debug("enter BusProvider.run")
+
+        self._bus.publish(
+            REVPI_DBUS_NAME,
+            InterfacePiControl(),
+        )
+
+        self._loop.run()
+        log.debug("leave BusProvider.run")
+
+    def stop(self):
+        log.debug("enter BusProvider.stop")
+        self._loop.quit()
+        log.debug("leave BusProvider.stop")