Let's help user to register :)

We should implement the methods:

• registerUser() in UserService class
• validate() in PasswordValidator class

Method validate() should compare the password with repeatPassword and check if their length is more or equal to 10. If not, throw exception PasswordValidationException with message "Wrong passwords" (since it's our custom logic, let's create our own, CHECKED, exception because user can put any password and our service shouldn't be broken. We should handle not-valid case and return the understandable message).

Method registerUser() should call the method validate() and handle the exception. If everything is ok, save user to the database (use method saveUser()), if not, print the message "Your passwords are incorrect. Try again.".