Add: EventBus class for event handling and subscription management

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/network/EventBus.java

@@ -0,0 +1,23 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.network;
+
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.function.Consumer;
+
+public class EventBus {
+    private final Map<Class<?>, List<Consumer<Object>>> handlers = new ConcurrentHashMap<>();
+
+    public <T> void subscribe(Class<T> eventType, Consumer<T> handler) {
+        handlers.computeIfAbsent(eventType, k -> new CopyOnWriteArrayList<>())
+                .add((Consumer<Object>) handler);
+    }
+
+    public <T> void publish(T event) {
+        List<Consumer<Object>> subscribers = handlers.get(event.getClass());
+        if (subscribers != null) {
+            subscribers.forEach(h -> h.accept(event));
+        }
+    }
+}