public BookLending lendBook(Book book, Customer customer) {
BookLending bookLending = new BookLending();
bookLending.setBook(book);
bookLending.setCustomer(customer);
bookLending.setLendingDate(new GregorianCalendar().getTime());
bookLending.setBookIsLended(true);
em.persist(bookLending);
return bookLending;
}
