public async Task<string> Handle(BookOrderCommand request, CancellationToken cancellationToken)
 {
     logger.LogInformation("start book order ...");
     var orderId = await bookOrderService.OrderBook(request.BookOrder);
     await Task.Delay(1000);
     await mediator.Publish(new BookOrderedEvent { OrderId = orderId });
     return orderId;
 }