handler.cs

public class PickupHandler : IRequestHandler<Pickup>
{
    private readonly IShipmentRepository _shipmentRepository;

    public PickupHandler(IShipmentRepository shipmentRepository)
    {
        _shipmentRepository = shipmentRepository;
    }

    public async Task<Unit> Handle(Pickup request, CancellationToken cancellationToken)
    {
        var shipment = await _shipmentRepository.Get(request.ShipmentId);
        shipment.Pickup(request.StopId, request.Departed);

        await _shipmentRepository.Save(shipment);

        return Unit.Value;
    }
}