Add `wiki-js` recipe

[drupol]

Hi,

This is my first PR in this project.

Let me know if:

1. Such thing is the right place
2. If it worth adding it here
3. If it worth it, should I change anything?

[fricklerhandwerk]

@Drupol thanks for the PR! I think generally it's a great idea to present such example setups. Yours is particularly well-written in my opinion.

Your proposal prompts the @NixOS/documentation-team to finally think in all seriousness about how to deal with those more generally. We've briefly discussed it before, but came to no conclusion because there were more pressing issues.

Here are some considerations:

• Here on nix.dev such samples will eventually go stale, it would in principle be better to keep them next to the code (same problem as with Wikis in general)
• There are no conventions or infrastructure to accommodate this in Nixpkgs. The closest seems to be pkgs/by-name, but there is currently no pattern to handle modules.
  • I can imagine your text to be in the README.md of the package's directory, and it would be a good example to build upon. It would mean though, that for a while no one will be able to find it because there are no hints and facilities for this.
• We can merge it as is, just to have a place for it now, but it will just postpone systematically dealing with a question I think is important already in the mid-term

[infinisil]

I generally think that NixOS modules should ideally Just Work™ with enable = true. Could the wiki-js module be made to work that way too?

[drupol]

@fricklerhandwerk: I've developed a recipe that I believe could be beneficial to others in our community. Initially, I considered sharing it on https://nixos.wiki, but given that it's not an official platform, I'd prefer to centralize the documentation in a more official location. This led to my decision to submit a PR here. I'm open to suggestions on the best place to share this information. Once I have your guidance, I'll make the necessary adjustments to ensure it's posted in the most appropriate place.

@infinisil: It seems that the feature isn't currently enabled (nixos/module). I agree that activating it would be interesting. I'm willing to explore this further and will look into what can be done to implement this idea.