Add possibility to use custom handlers on 'handleReceivedMessage'

android/src/main/java/com/dieam/reactnativepushnotification/modules/RNReceivedMessageCustomHandler.java

@@ -0,0 +1,7 @@
+package com.dieam.reactnativepushnotification.modules;
+
+import android.os.Bundle;
+
+public interface RNReceivedMessageCustomHandler {
+    void onMessageReceived(Bundle bundle);
+}

android/src/main/java/com/dieam/reactnativepushnotification/modules/RNReceivedMessageHandler.java

@@ -23,6 +23,7 @@
 
 import org.json.JSONObject;
 
+import java.util.ArrayList;
 import java.util.Map;
 import java.util.List;
 import java.security.SecureRandom;
@@ -33,6 +34,8 @@
 public class RNReceivedMessageHandler {
     private FirebaseMessagingService mFirebaseMessagingService;
 
+    public static List<RNReceivedMessageCustomHandler> CustomHandlers = new ArrayList();
+
     public RNReceivedMessageHandler(@NonNull FirebaseMessagingService service) {
         this.mFirebaseMessagingService = service;
     }
@@ -128,6 +131,10 @@ public void handleReceivedMessage(RemoteMessage message) {
 
         Log.v(LOG_TAG, "onMessageReceived: " + bundle);
 
+        for (RNReceivedMessageCustomHandler handler : CustomHandlers) {
+            handler.onMessageReceived(bundle);
+        }
+
         // We need to run this on the main thread, as the React code assumes that is true.
         // Namely, DevServerHelper constructs a Handler() without a Looper, which triggers:
         // "Can't create handler inside thread that has not called Looper.prepare()"