fetchHistory method
Ask for older messages than the ones we hold.
With no beforeMsgid, this asks for the most recent, which is what a fresh window wants.
Implementation
void fetchHistory(String target, {String? beforeMsgid, int limit = 50}) {
_alive();
command({
'type': 'fetch_history',
'target': target,
'before_msgid': beforeMsgid,
'limit': limit,
});
}