android: add definitions for the DeviceSerialNumber MDM key

Updates tailscale/tailscale#16010

Signed-off-by: Anton Tolchanov <anton@tailscale.com>

android/src/main/java/com/tailscale/ipn/mdm/MDMSettings.kt

@@ -59,6 +59,10 @@ object MDMSettings {
   val postureChecking =
       AlwaysNeverUserDecidesMDMSetting("PostureChecking", "Enable Posture Checking")
 
+  // Handled on the backend
+  val deviceSerialNumber =
+      StringMDMSetting("DeviceSerialNumber", "Serial number of the device that is running Tailscale")
+
   val useTailscaleDNSSettings =
       AlwaysNeverUserDecidesMDMSetting("UseTailscaleDNSSettings", "Use Tailscale DNS Settings")
 

android/src/main/res/values/strings.xml

@@ -205,6 +205,8 @@
     <string name="hides_the_specified_categories_of_network_devices_from_the_devices_list_in_the_client">Hides the specified categories of network devices from the devices list in the client.</string>
     <string name="allow_lan_access_when_using_an_exit_node">Allow LAN access when using an exit node</string>
     <string name="enable_posture_checking">Enable posture checking</string>
+    <string name="device_serial_number">Serial number of the device that is running Tailscale</string>
+    <string name="device_serial_number_descr">Allows administrators to pass the serial number of the device to Tailscale client using MDM.</string>
     <string name="use_tailscale_dns_settings">Use Tailscale DNS settings</string>
     <string name="use_tailscale_subnets">Use Tailscale subnets</string>
     <string name="allow_incoming_connections">Allow incoming connections</string>

android/src/main/res/xml/app_restrictions.xml

@@ -66,6 +66,12 @@
         android:restrictionType="choice"
         android:title="@string/enable_posture_checking" />
 
+    <restriction
+        android:description="@string/device_serial_number_descr"
+        android:key="DeviceSerialNumber"
+        android:restrictionType="string"
+        android:title="@string/device_serial_number" />
+
     <restriction
         android:entries="@array/always_never_userdecides_labels"
         android:entryValues="@array/always_never_userdecides"