get_notification_preferences
Reads your email preferences. Takes no arguments.
Returns digestScope, hotelMessageEmails and supportReplyEmails. A person
who never changed a preference gets the defaults: "stage", true and
true.
update_notification_preferences
Prepares a change to your email preferences. Only the fields you send change.
Nothing is saved until
confirm_change runs after you said
yes.
If the values you send are already saved, nothing is prepared. If a preference
changes before the confirm, the confirm changes nothing and asks you to
prepare again.