public async Task <IActionResult> CreateTentative([FromBody] CreateTentativeReservationRequest request)
        {
            Guard.Against.Null(request, nameof(request));

            var reservationId = idGenerator.New();

            var command = CreateTentativeReservation.Create(
                reservationId,
                request.SeatId
                );

            await commandBus.Send(command);

            return(Created("api/Reservations", reservationId));
        }
    public async Task <IActionResult> CreateTentative([FromBody] CreateTentativeReservationRequest request)
    {
        if (request == null)
        {
            throw new ArgumentNullException(nameof(request));
        }

        var reservationId = idGenerator.New();

        var command = CreateTentativeReservation.Create(
            reservationId,
            request.SeatId
            );

        await commandBus.Send(command);

        return(Created("api/Reservations", reservationId));
    }