Add helper for obtaining fields

Author: aurimasc

com.unity.mobile.notifications/Runtime/Android/AndroidNotificationCenter.cs

@@ -5,8 +5,10 @@
 
 #if UNITY_2022_2_OR_NEWER
     using JniMethodID = System.IntPtr;
+    using JniFieldID = System.IntPtr;
 #else
     using JniMethodID = System.String;
+    using JniFieldID = System.String;
 #endif
 
 namespace Unity.Notifications.Android
@@ -473,6 +475,18 @@ public JniApi(AndroidJavaClass notificationManagerClass, AndroidJavaObject notif
             Bundle.CollectJni();
         }
 
+        public static JniFieldID FindField(AndroidJavaClass clazz, string name, string signature, bool isStatic)
+        {
+#if UNITY_2022_2_OR_NEWER
+            var field = AndroidJNIHelper.GetFieldID(clazz.GetRawClass(), name, signature, isStatic);
+            if (field == IntPtr.Zero)
+                throw new Exception($"Field {name} with signature {signature} not found");
+            return field;
+#else
+            return name;
+#endif
+        }
+
         public static JniMethodID FindMethod(AndroidJavaClass clazz, string name, string signature, bool isStatic)
         {
 #if UNITY_2022_2_OR_NEWER