Improve unattended system upgrades

[simonwacker]

• Send emails about upgrades using https://wiki.debian.org/UnattendedUpgrades#apt-listchanges
• Use the designated role https://github.com/jnv/ansible-role-unattended-upgrades
• Take some inspiration about better configuration from https://haydenjames.io/how-to-enable-unattended-upgrades-on-ubuntu-debian/
• Maybe additional to or instead of unattended-upgrades use
  • Ansible apt for system upgrades as described in https://www.cyberciti.biz/faq/ansible-apt-update-all-packages-on-ubuntu-debian-linux/ or https://www.redpill-linpro.com/sysadvent/2017/12/24/ansible-system-updates.html
  • One of the alternatives described in https://help.ubuntu.com/community/AutoWeeklyUpdateHowTo or https://help.ubuntu.com/community/AutomaticSecurityUpdates like cron-apt or Anacron