service: Split most code into a static helper library
service: Split most code into a static helper library

This will make unit testing the code easier.

Signed-off-by: Philip Withnall <29c2a2ac2a854b9cf047275aa9de346d096be2e0@endlessm.com>

GNOME/dconf,GNOME/dconf,GNOME/dconf,GNOME/dconf