Enhance documentation regarding internal icinga config sync check

[ChrLau]

Hi,

I had the problem that I converted my non-distributed monitoring to a distributed one. That worked fine for years, but due to a new NotificationCommand I noticed that I had defined a necessary Token inside /etc/icinga2/constants.conf file, which of course is not synced to the satellites/agents. I only noticed this a few weeks after these changes, as another new service check wasn't being rolled out to the agents. (Small homelab environment, not many changes are happening.)

After figuring this all out I learned only through the Community forum that the internal icinga CheckCommand checks for successful config syncs IF it is executed on the satellites/agents. Which was not the case in my scenario as I didn't properly migrate that service for a redundant setup.

However.. The documentation on this is very sparse. The config file sync check is only named indirectly and you only understand what that means when you already know what the CheckCommand does. - Not really helpful. Also the troubleshooting section made no mention of that.

With this commit I try to fix these 2 minor issues. Hoping other people will spot their errors faster than me. ;-)

[ChrLau]

I wasn't sure if I should mention the icinga CheckCommand in the technical concept describing the config sync. However I'm pleased to do so if you think it makes sense: https://icinga.com/docs/icinga-2/latest/doc/19-technical-concepts/#config-sync

[ChrLau]

Hi @oxzi

the changes are fine for me. And I added myself to the AUTHORS file.

Thank you!

[ChrLau]

@oxzi No worries! Thanks for taking the time!