Identifier of a message in the chat with the giveaway; the message could have been deleted.
Optionalis_True, if the giveaway was completed, but no user won the prize.
Optionalprize_The number of Telegram Stars to be split among giveaway winners.
Source of the boost, always 'giveaway'.
OptionaluserUser that won the prize in the giveaway if any.
See
Telegram Bot API: ChatBoostSourceGiveaway