Add: CommandHandler interface for executing requests

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

@@ -0,0 +1,7 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.network.command;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.parser.Request;
+
+public interface CommandHandler {
+    void execute(Request request);
+}