docs: public synchronized TrackedTorrent announce(TrackedTorrent torrent) {
      TrackedTorrent existing = myTorrentsRepository.getTorrent(torrent.getHexInfoHash());
  
      if (existing != null) {
        logger.warn("Tracker already announced torrent with hash {}.", existing.getHexInfoHash());
        return existing;
      }
  
      myTorrentsRepository.putIfAbsent(torrent.getHexInfoHash(), torrent);
      logger.info("Registered new torrent with hash {}.", torrent.getHexInfoHash());
      return torrent;
    }