async function getCustomLink(userId) {
  if (!this.bot) {
    throw new ServiceNotConfiguredError('Telegram not configured');
  }
  const telegramBotInfos = await this.bot.getMe();
  const { apiKey } = await generateApiKey();
  this.gladys.cache.set(`${CACHE_KEY_BASE}:${apiKey}`, userId);
  const link = `https://telegram.me/${telegramBotInfos.username}?start=${apiKey}`;
  return link;
}
@description Get custom link.
@param {string} userId - The user requesting the link.
@returns {Promise<string>} Resolve with URL.
@example
const link = await getCustomLink();