cancel method
Cancel a pending request by id.
Implementation
bool cancel(String id, [String? reason]) {
final pending = _pending.remove(id);
if (pending == null) return false;
pending.timer?.cancel();
pending.completer.completeError(
BridgeError(
code: ErrorCode.requestCancelled,
message: reason ?? 'Request $id cancelled',
),
);
return true;
}