Minor change, implemented trivial toString()

broker/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/events/ProtocolEvent.java

@@ -1,5 +1,6 @@
 package org.dna.mqtt.moquette.messaging.spi.impl.events;
 
+import org.dna.mqtt.moquette.proto.Utils;
 import org.dna.mqtt.moquette.proto.messages.AbstractMessage;
 import org.dna.mqtt.moquette.server.ServerChannel;
 
@@ -22,4 +23,9 @@ public class ProtocolEvent extends MessagingEvent {
     public AbstractMessage getMessage() {
         return message;
     }
+    
+    @Override
+    public String toString() {
+        return "ProtocolEvent wrapping " + Utils.msgType2String(message.getMessageType());
+    }
 }