public async Task <ShopOperationResult> CreateAsync(PurchaseInvoice item)
 {
     if (item == null)
     {
         throw new ArgumentNullException(nameof(item));
     }
     _db.PurchaseInvoices.Add(item);
     try
     {
         await _db.SaveChangesAsync();
     }
     catch
     {
         return(ShopOperationResult.Failed(_errorDescriber.DefaultError()));
     }
     return(ShopOperationResult.Success);
 }