Tracking of technical details of using shoutrrr

[favonia]

This is to track the technical details to implement #532 using shoutrrr.

• How to display all services in a RouterService (not all available services)?
• Should we set the title (or other params?)

PRs

• Part 1: feat: link shoutrrr and initialize services (part 1 of shoutrrr support) #633
• Part 2: refactor: move message generation to updater (part 2 of shoutrrr support) #640
• Part 2.5: Rework the message structure
• Part 3: Actually send notifications
• Part 4: Adjust message formats to match Design of monitor/notifier messages #641
• Part 5: Testing on real machines

Message

Current plan: These will be notified:

• Starting of the program unless it's one-time
• Configuration errors
• Use of deprecated settings (?)
• IP detection error (every time!)
• IP changes
• Successful detection of the same IP after failures (?)
• Failures to update DNS records
• Exiting of the program unless it's one-time

These will not be notified:

• Failure to ping monitors