Manage update timing outside of the app

[Feichtmeier]

Instead of using a timer inside package_service.dart we want to use systemd for update check timer

TODO

• [ ] #349
• [ ] Use systemd for update check timer
• [ ] add a specific arg to launch the app in main.dart with the updates page selected
• [ ] connect the snap and systemd
• [ ] https://github.com/ubuntu-flutter-community/software/issues/369

Example taken from https://opensource.com/article/20/7/systemd-timers

Create the following myMonitor.service unit file in the /etc/systemd/system directory. It does not need to be executable:

# This service unit is for testing timer units
# By David Both
# Licensed under GPL V2
#

[Unit]
Description=Logs system statistics to the systemd journal
Wants=myMonitor.timer

[Service]
Type=oneshot
ExecStart=/usr/bin/free

[Install]
WantedBy=multi-user.target

create a timer unit file, myMonitor.timer in /etc/systemd/system, and add the following:

# This timer unit is for testing
# By David Both
# Licensed under GPL V2
#

[Unit]
Description=Logs some system statistics to the systemd journal
Requires=myMonitor.service

[Timer]
Unit=myMonitor.service
OnCalendar=*-*-* *:*:00

[Install]
WantedBy=timers.target