Android: Exercise: Bookstore REST PUT

In this exercise you must add to the BookStore REST application, so that users can change the information (title, price, etc.) on a book.

The application is almost ready: It has all the necessary GUI (I think), but when the user presses the Update button, nothing happens.
You must make something happen: Update the back-end.

Send an HTTP PUT request with a relevant JSON document in the body (try it with Postman before you add it to the application).