Change behavior: remove 'password' method from the ChangeEmail service object. Add 'token' and 'expires_at' methods to the model.
Change behavior: remove all public attributes from the ConfirmEmail model.
Change in behavior: remove unnecessary public attributes from the SignUp service object model. Add 'token' and 'expires_at' public attributes instead.
Test coverage: add specs to check if all the necessary attributes is acceptible for mass assignment.