Updating the ReviewFormViewController class to save reviews

The Save button in the Review Form screen currently just prints the review to the Debug area when tapped. To save reviews, you'll need to modify the onSaveTapped(_:) method to save a review to the persistent store when the Save button is tapped. Follow these steps:

1. Click the ReviewFormViewController file in the Project navigator. Add the following property to the ReviewFormViewController class before the outlet declarations to store the restaurant identifier:

   var selectedRestaurantID: Int?

2. Create a private extension, move the onSaveTapped(_:) method into it, and modify it as follows:

   private extension ReviewFormViewController {
      @IBAction func onSaveTapped(_ sender: Any) {
         var reviewItem = ReviewItem() 
         reviewItem.rating = ratingsView.rating
         reviewItem.title = titleTextField.text
    ...