party service: check joins are for the current party

The server can resume party membership on handshake to parties other
than the current client party (eg. if the client is restarted or for any
other reason the current party changes). This desyncs otherwise if the
joins aren't checked to be in the current party.

http-api/src/main/java/net/runelite/http/api/ws/messages/party/UserJoin.java

@@ -34,5 +34,6 @@ import net.runelite.http.api.ws.WebsocketMessage;
 public class UserJoin extends WebsocketMessage
 {
 	private final UUID memberId;
+	private final UUID partyId;
 	private final String name;
 }