Refactor how handlers encode messages

src/main/java/emu/nebula/server/routes/AgentZoneHandler.java

@@ -242,7 +242,7 @@ public class AgentZoneHandler implements Handler {
                     var handler = new NetHandler() {
                         @Override
                         public byte[] handle(GameSession session, byte[] message) throws Exception {
-                            return this.encodeMsg(failedAckId);
+                            return PacketHelper.encodeMsg(failedAckId);
                         }
                     };
                     

src/main/java/emu/nebula/server/routes/UserSetDataHandler.java

@@ -42,7 +42,6 @@ public class UserSetDataHandler extends UserLoginHandler {
         ctx.result("{\"Code\":200,\"Data\":{},\"Msg\":\"OK\"}");
     }
     
-    @SuppressWarnings("unused")
     private static class UserSetDataReqJson {
         public String Key;
         public String Value;