Addressee: make birthday writable from QML
Add a private Addressee::setBirthdayProperty(const QDateTime &) wrapper method that guesses the extra withTime argument and use that as the WRITE method for the Q_PROPERTY birthday.
A non-midnight time spec will lead to the birthday being recorded with the time, a time spec exactly at midnight to a date-only birthday (the common case). This is the best we can do for a property setter.
This should make setting the birthday in Plasma Phonebook work again. (It last worked when Plasma Phonebook had its own QML wrapper for the Addressee class, which has been dropped since.)