Daemon: move funcs that are backend agnostic to their own object

daemon/CommonBackend.vala

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2021-2026 elementary, Inc. (https://elementary.io)
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+[DBus (name = "io.elementary.InstallerDaemon")]
+public class InstallerDaemon.CommonBackend : GLib.Object {
+    public void set_demo_mode_locale (string locale) throws GLib.Error {
+        GLib.FileUtils.set_contents ("/etc/default/locale", "LANG=" + locale);
+    }
+
+    public void trigger_demo_mode () throws GLib.Error {
+        var demo_mode_file = GLib.File.new_for_path ("/var/lib/lightdm/demo-mode");
+        try {
+            demo_mode_file.create (GLib.FileCreateFlags.NONE);
+        } catch (GLib.Error e) {
+            if (!(e is GLib.IOError.EXISTS)) {
+                throw e;
+            }
+        }
+    }
+}

daemon/Daemon.vala

@@ -15,6 +15,7 @@ public class InstallerDaemon.Application : GLib.Application {
         base.dbus_register (connection, object_path);
 
         try {
+            connection.register_object ("/io/elementary/InstallerDaemon", new InstallerDaemon.CommonBackend ());
     #if DISTINST_BACKEND
             connection.register_object ("/io/elementary/InstallerDaemon", new InstallerDaemon.DistinstBackend ());
     #endif

daemon/DistinstBackend.vala

@@ -219,21 +219,6 @@ public class InstallerDaemon.DistinstBackend : GLib.Object {
         });
     }
 
-    public void set_demo_mode_locale (string locale) throws GLib.Error {
-        GLib.FileUtils.set_contents ("/etc/default/locale", "LANG=" + locale);
-    }
-
-    public void trigger_demo_mode () throws GLib.Error {
-        var demo_mode_file = GLib.File.new_for_path ("/var/lib/lightdm/demo-mode");
-        try {
-            demo_mode_file.create (GLib.FileCreateFlags.NONE);
-        } catch (GLib.Error e) {
-            if (!(e is GLib.IOError.EXISTS)) {
-                throw e;
-            }
-        }
-    }
-
     private string casper_dir () {
         const string CDROM = "/cdrom";
 

daemon/meson.build

@@ -1,4 +1,5 @@
 vala_files = [
+    'CommonBackend.vala',
     'Daemon.vala',
     common_files
 ]