A few itmes deserve to be mentioned:
- use apg to generate random password when install.
- generated password won't get updated when upgrading / reinstall.
- add more to description to make lintian happy.
- generated Makefile.am don't need to be listed in debian/copyright.
- the way of installing systemd service is changed. Thanks to advice
from Boyuan.
- multi-arch can be archived without specific setting in debian/rules
- add debian/watch file