* Add migrations to ensure password hash is synced across users & user_passwords
* Persist password-related data in user_passwords instead of users
* Merge User#expire_old_email_tokens with User#expire_tokens_if_password_changed
* Add post deploy migration to mark password-related columns from users table as read-only
* Refactored UserPassword#confirm_password? and changes required to accommodate hashing the password after validations
