Add debug logging for notifications (#861)

Author: acoburn

notifications/reactive/src/main/java/org/trellisldp/reactive/ReactiveEventService.java

@@ -17,6 +17,7 @@
 
 import static java.util.Objects.requireNonNull;
 import static org.eclipse.microprofile.reactive.messaging.Message.of;
+import static org.slf4j.LoggerFactory.getLogger;
 
 import io.reactivex.BackpressureStrategy;
 import io.reactivex.Flowable;
@@ -27,6 +28,7 @@
 
 import org.eclipse.microprofile.reactive.messaging.Message;
 import org.eclipse.microprofile.reactive.messaging.Outgoing;
+import org.slf4j.Logger;
 import org.trellisldp.api.*;
 
 /**
@@ -35,6 +37,8 @@
 @ApplicationScoped
 public class ReactiveEventService implements EventService {
 
+    private static final Logger LOGGER = getLogger(ReactiveEventService.class);
+
     public static final String REACTIVE_DESTINATION = "trellis";
 
     private final EventSerializationService serializer;
@@ -61,6 +65,7 @@ public ReactiveEventService(final EventSerializationService serializer) {
 
     @Override
     public void emit(final Event event) {
+        LOGGER.debug("Sending message to reactive destination: {}", event.getIdentifier());
         subject.onNext(of(serializer.serialize(event)));
     }