@RequestMapping(value = "/library/add", method = RequestMethod.GET)
public String addBookToLibrary(@RequestParam(required = true) String id) {
User user = (User) ProfileController.getAuthenticatedUser();
if (user.getBooks() == null || !user.getBooks().contains(id)) user.addBook(id);
userService.save(user);
ProfileController.authenticateUser(user);
return "redirect:/library";
}
