Add publiccode.yml

[bobapple]

Introduce publiccode.yml with project metadata and public administration compliance information.

publiccode.yml is a metadata standard for repositories containing software developed or acquired by the Public Administration, aimed at making them easily discoverable and thus reusable by other entities.

Reference to the standard: https://yml.publiccode.tools/schema.core.html

[julianbrost]

A reference to a specification for that file format would be nice,

Also, what's the scope of that file, as in is it just Icinga 2 or is it supposed to describe Icinga as a whole? URL says icinga2, but other parts of the file describe more than what Icinga 2 does on its own.

[julianbrost]

For v2.16, that should now be:

Suggested change

	license: GPL-2.0-or-later
	license: GPL-3.0-or-later

[bobapple]

This file will be automatically fetched so it should represent the current state, otherwise "wrong" information would be displayed. I'm aware that I will have to update this once v2.16 is released.

[julianbrost]

So another issue for that: #10724 🤷

[bobapple]

I updated the PR comment to include a reference to the specification.

The scope is kind of mixed. The EU Open Source Catalogue maintainers require that we have this file in a public git repository so that they can programmatically fetch the information. My suggestion to add this file to icinga.com was declined. They want to have it in the icinga2 repo since they see it as the "major" repository of Icinga. Therefore I had to add some references to Icinga 2 as well. But generally it describes Icinga as a whole. I'm not super happy with this approach but it's the only way currently.

[julianbrost]

Note: for a quick validation, uploading the file to https://publiccode-editor.developers.italia.it/ (as linked on https://yml.publiccode.tools/index.html) and checking if there are any changes is helpful, at least a bit (it doesn't give an error, it just silently discards what doesn't fit the standard)