OptionalpayloadType-specific reaction data. For "emoji_reaction" reactions, contains an emoji key with the Unicode emoji string (e.g., "👍").
Reaction type identifier. Currently always "emoji_reaction" for emoji-based reactions.
OptionaluserPublic ID of the user who added the reaction (usr_...).
A compact reaction record embedded in a message's
reactionsarray, representing a single user's reaction to a message.