The payload of :guild_scheduled_event_user_add and :guild_scheduled_event_user_remove: a user subscribed to a scheduled event, or stopped.
:guild_scheduled_event_user_add
:guild_scheduled_event_user_remove
@type t() :: %Lingo.Event.ScheduledEventUser{ guild_id: String.t(), guild_scheduled_event_id: String.t(), user_id: String.t() }