[KandraDocumentEntity]
public partial class Waybill : DocumentBase, IEntityWithRows<WaybillRow>
{
    public override string Code { get; set; } = "";
    public override DateTime DateTime { get; set; }
    public Guid CounterpartyId { get; set; }
    public Guid WarehouseId { get; set; }
    public List<WaybillRow> Rows { get; set; } = [];
}

// Registers are written only inside a posting scope.
public class WaybillBehavior : DocumentBehavior<Waybill, WaybillDto>
{
    public override async ValueTask OnSubmitAsync(Waybill doc, ISubmitScope scope)
    {
        var inventory = scope.GetWriter<IInventoryRegisterWriter>();
        foreach (var row in doc.Rows)
            await inventory.ExpenseAsync(doc, row.ItemId, doc.WarehouseId, row.Quantity);
    }
}

// Controllers, API client, EF config, DI, Blazor pages: generated.