builder.Entity<MAOrder>().HasMany(x => x.Positions).WithOne(x => x.Order).OnDelete(DeleteBehavior.SetNull);
builder.Entity<MAOrder>().HasOne(x => x.Counterparty).WithMany(x => x.Orders).OnDelete(DeleteBehavior.SetNull);
builder.Entity<MAOrderStatus>().HasMany(x => x.Orders).WithOne(x => x.Status).OnDelete(DeleteBehavior.SetNull);
builder.Entity<MAOrderStatus>().HasMany(x => x.Positions).WithOne(x => x.Status).OnDelete(DeleteBehavior.SetNull);
builder.Entity<MAOrderCategory>().HasMany(x => x.Positions).WithOne(x => x.Category).OnDelete(DeleteBehavior.SetNull);
builder.Entity<MAPaymentType>().HasMany(x => x.Orders).WithOne(x => x.PaymentType).OnDelete(DeleteBehavior.SetNull);
builder.Entity<ApplicationUser>().HasMany(x => x.CreatedOrders).WithOne(x => x.Creator).OnDelete(DeleteBehavior.SetNull);
builder.Entity<ApplicationUser>().HasMany(x => x.CompletedOrders).WithOne(x => x.Worker).OnDelete(DeleteBehavior.SetNull);