Get Andoid Id

https://answers.unity.com/questions/430630/how-can-i-get-android-id-.html

 AndroidJavaClass clsUnity = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
 AndroidJavaObject objActivity = clsUnity.GetStatic("currentActivity");
 AndroidJavaObject objResolver = objActivity.Call("getContentResolver");
 AndroidJavaClass clsSecure = new AndroidJavaClass("android.provider.Settings$Secure");
 string android_id = clsSecure.CallStatic("getString", objResolver, "android_id");