nixosTests.ldap: remove

[flokli]

Motivation for this change

This tests seem to have worked in 15f105d, but
broke somewhere in the meantime.

The current module doesn't seem to be generally usable and might need a
serious refactor. It requires quite some hacks to get it to work (see
#86305 (comment)),
or how the test used systemd.services.openldap.preStart and made quite
some assumptions on internals.

On top of that, the test has been broken since 2020-01-12 (5 months), so
there's no guarantee this works at all.

Let's drop the test and throw a big deprecation warning to alert
everyone still using the module, and if nobody speaks up, remove it as well.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[Ekleog]

As per #86305 (comment), the module works pretty well for basic usage, though maybe (I've never administered a complex LDAP server) it isn't adapted to complex use cases.

So IMO if we just deprecate/remove this without proposing anything better, we then lose the “simple” use case just working, and don't get the complex use cases working any better. I'm not sure what this would thus bring, though I totally understand that with the information available before my comment there it was the only reasonable thing to do :)

[flokli]

As per #86305 (comment), if there's a more simpler way to test basic functionality, such a VM test would help to verify (some) things are still working.

Would you be willing to add a simple VM test on top?

[Mic92]

I can add a basic test based on my server: https://github.com/Mic92/dotfiles/blob/master/nixos/eve/modules/openldap.nix#L14

[flokli]

@Mic92 thanks! In that case, feel free to ping me on the PR :-)

[flokli]

@Mic92 I pushed a new commit that only removes the broken VM tests, and adds you as a maintainer to the openldap module. The openldap.nix vm test is left as it is (and was all the time)