Implement setting disc music as main theme

src/main/java/emu/nebula/server/handlers/HandlerPlayerMusicSetReq.java

@@ -2,6 +2,7 @@ package emu.nebula.server.handlers;
 
 import emu.nebula.net.NetHandler;
 import emu.nebula.net.NetMsgId;
+import emu.nebula.proto.Public.I64;
 import emu.nebula.net.HandlerId;
 import emu.nebula.net.GameSession;
 
@@ -10,7 +11,18 @@ public class HandlerPlayerMusicSetReq extends NetHandler {
 
     @Override
     public byte[] handle(GameSession session, byte[] message) throws Exception {
-        return session.encodeMsg(NetMsgId.player_music_set_failed_ack);
+        // Parse request
+        var req = I64.parseFrom(message);
+        
+        // Set music
+        boolean success = session.getPlayer().setMusic(req.getValue());
+        
+        if (success == false) {
+            return session.encodeMsg(NetMsgId.player_music_set_failed_ack);
+        }
+        
+        // Encode and send
+        return session.encodeMsg(NetMsgId.player_music_set_succeed_ack);
     }
 
 }