feat(dbus): Add Bluetooth configuration functionality

Introduce functionality to enable, disable, and check the status and
availability of Bluetooth devices using the `configure_bluetooth`
method. Integrate Bluetooth configuration into the feature management
system by mapping it in `interface_config.py`.

src/revpi_middleware/dbus_middleware1/system_config/revpi_config.py

@@ -20,6 +20,7 @@ log = getLogger(__name__)
 
 ConfigVariable = namedtuple("ConfigVariable", ["name", "value", "line_index"])
 
+LINUX_BT_CLASS_PATH = "/sys/class/bluetooth"
 LINUX_WIFI_CLASS_PATH = "/sys/class/ieee80211"
 CONFIG_TXT_LOCATIONS = ("/boot/firmware/config.txt", "/boot/config.txt")
 
@@ -212,6 +213,40 @@ def configure_avahi_daemon(action: ConfigActions):
     return return_value
 
 
+def configure_bluetooth(action: ConfigActions):
+    hci_device = join(LINUX_BT_CLASS_PATH, "hci0")
+    bt_rfkill_index = get_rfkill_index(hci_device)
+
+    # If the bluetooth device is not present, the device should have been
+    # brought up by revpi-bluetooth's udev rules or vendor magic (devices
+    # based on CM4 and newer). Nothing we can do here, so treat the interface
+    # as disabled.
+
+    if action is ConfigActions.ENABLE:
+        if bt_rfkill_index is not None:
+            subprocess.call(["rfkill", "unblock", str(bt_rfkill_index)])
+
+    elif action is ConfigActions.DISABLE:
+        if bt_rfkill_index is not None:
+            subprocess.call(["rfkill", "block", str(bt_rfkill_index)])
+
+    elif action is ConfigActions.STATUS:
+        if bt_rfkill_index is None:
+            return False
+
+        with open(f"/sys/class/rfkill/rfkill{bt_rfkill_index}/soft", "r") as f:
+            buffer = f.read().strip()
+            return buffer == "0"
+
+    elif action is ConfigActions.AVAILABLE:
+        return bt_rfkill_index is not None
+
+    else:
+        raise ValueError(f"action {action} not supported")
+
+    return None
+
+
 def configure_con_can(action: ConfigActions):
     revpi = RevPiConfig()
     if action is ConfigActions.AVAILABLE: