public static AuctionReadModel AddAuction(
            this InMemoryReadStore store,
            AuctionId auctionId        = null,
            string name                = null,
            DateTimeOffset?auctionDate = null)
        {
            var entry = store.Add(new AuctionReadModel
            {
                Id          = auctionId ?? new AuctionId(),
                Name        = name ?? $"{Guid.NewGuid()}",
                AuctionDate = auctionDate.GetValueOrDefault(DateTimeOffset.UtcNow)
            });

            store.SaveChanges();
            return(entry.Entity);
        }
        public static AuctionItemReadModel AddAuctionItem(
            this InMemoryReadStore store,
            AuctionId auctionId,
            string name,
            string donor       = null,
            string description = null,
            int quantity       = 1)
        {
            var entry = store.Add(new AuctionItemReadModel
            {
                Description = description,
                Donor       = donor,
                AuctionId   = auctionId,
                Name        = name,
                Quantity    = quantity
            });

            store.SaveChanges();
            return(entry.Entity);
        }