[ENH] registrationDate should be updated on account confirmation (i.e. when account is approved) to accurately reflect when user became registered user

For all practical purposes, when the user account is confirmed (e.g. when the admin approves the user registration), the time that happens should then be considered the registrationDate, especially since the created date (which would be the original registration date) is stored as well. Sometimes approval can take a while. If this is not updated it would not be accurate when the user actually became a registered user.