/// <summary>
        /// Renames a product.
        /// </summary>
        /// <param name="id">Product's key.</param>
        /// <param name="newName">New name for a product.</param>
        public void RenameProduct(int id, string newName)
        {
            ValidatorClass.CheckProductById(id);
            ValidatorClass.StringValidator(newName);

            Storage.products[id].Name = newName;
        }
        /// <summary>
        /// Changes the price of a specific item in the product storage.
        /// </summary>
        /// <param name="id">Product's key.</param>
        /// <param name="price">Product's new price.</param>
        public void ChangePrice(int id, decimal newPrice)
        {
            ValidatorClass.CheckProductById(id);
            ValidatorClass.PriceValidator(newPrice);

            Storage.products[id].Price = newPrice;
        }
        /// <summary>
        /// Deletes an item from the product storage.
        /// </summary>
        /// <param name="id">Product's key.</param>
        public void DeleteProduct(int id)
        {
            ValidatorClass.CheckProductById(id);

            Storage.products.Remove(id);
        }