public PackageService(
     ShipmentsDbContext dbContext,
     IEventBus eventBus,
     IProductAvailabilityService productAvailabilityService
     )
 {
     this.dbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
     this.eventBus  = eventBus ?? throw new ArgumentNullException(nameof(eventBus));
     this.productAvailabilityService = productAvailabilityService ??
                                       throw new ArgumentNullException(nameof(productAvailabilityService));
 }
 public ShipmentRepository(ShipmentsDbContext shipmentsContext)
 {
     _context = shipmentsContext;
 }