Improve configuration snippets for Icinga

[amotl]

Dear Frederic,

in order to improve installation convenience further, this time on the »Icinga integration« side, the goal of this patch [^1] is to provide complete Icinga configuration resources which can be reused out of the box. We verified it by running it on our servers already, which was needed to adjust some further bits. We hope you like it.

Features

• The configuration provides reasonable default threshold values (warning/critical) for the corresponding sensor modes. Please let me know if you think some of the default values can be improved.
• For addressing the Synology appliance, either host.vars.synology_host or $address$ is used.
• With host.vars.synology_location, you can optionally provide a human-readable label to the monitored appliance. This will get reflected as suffix to the display_name.
• Optionally enable command_endpoint = host_name for running the check program on a different host.
• Beside host.vars.os == "DSM", the check will also trigger on host.vars.check_synology == true. This is useful if the Service object is assigned to another, non-DSM, host.
• Provide reasonable inline documentation which describe the configuration parameters in more detail.

Screenshot

With kind regards, Andreas.

/cc @tonkenfo

[^1]: It is based upon my previous changes #20. For looking at the very diff right now instead of the PR which also includes the previous commits, 0b1eb8888c would be the right choice.

[amotl]

Any objections from your side?

It's ready.

Otherwise i will merge.

Go ahead. Thank you again!