When attempting to reserve a meal that's booked out, the response is HTTP 400, with response:

{
  "error": "ERROR_AMOUNT_LIMIT"
}

It would be great handle this case, instead of retrying. Also will empower #9, since we can differentiate between when to retry and when to fallback to second choice.
https://github.com/edmundmok/mealpy/blob/5fc5bc7a97e4dda452b26d46552c5fccf084ee0