nixos/pipewire: add configPackages options

[hcsch]

Description of changes

Added configPackages options to both services.pipewire and services.pipewire.wireplumber. Packages specified in these options have their relevant files (e.g. share/pipewire/pipewire.conf.d/*) combined in store path generated by pkgs.buildEnv and linked to /etc/.
Pipewire extraConfig options also get added to this store path in the appropriate locations.

Added extraLv2Packages options to the options of both services for packages providing lv2 plugins required by filter chains the user set up in their pipewire/wireplumber config files. These get added to the LV2_PATH of the service they were specified for. In addition, packages in configPackages can specify passthru.requiredLv2Packages to have them included in the path as well.

In the case of wireplumber, added config and lv2 packages get added for pipewire as well, since config packages for wireplumber are likely to have config files for pipewire as well.

For now my main use case for this is asahi-audio (my setup for that is not yet clean enough to upstream), but I'm sure that as time goes on, other packages will pop up to configure filter chains or similar things. With these options, adding them to nixpkgs should be easy and using them should be easy for users as well.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

I've tested these changes locally with my yet to be upstreamed asahi-audio package and the config files are put in the right places, and lv2 packages are found by wireplumber/pipewire. The existing nixos default config files for pipewire are also present.

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[hcsch]

Should I document the attribute in passthru somewhere for discoverabiltiy? If so, where is the most appropriate place for that?

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/asahi-audio-on-nixos-lv2-path-management/38569/4

[hcsch]

Forgot some mentions of the not yet upstreamed asahi-audio package in the option descriptions/examples. Those have been removed with the force-push

[hcsch]

@tpwrules If I'm right, you set up asahi-audio for https://github.com/tpwrules/nixos-apple-silicon. I'd be happy to hear if this looks useful to you :)

[tpwrules]

@K900 we had discussed something along these lines on Matrix, what do you think? I don't have any opinion yet.

[hcsch]

I moved some definitions around in the pipewire module to make the git diff a bit more readable. Adding a let ... in in the config definition and having to change the indentation accordingly kinda made the diff a bit messy. Hopefully this way it's nicer to review

Edit: Accidentally duplicated some systemd service settings while rebasing. Fixed that again just now

[K900]

Do we really need separate options for LV2 plugins on Wireplumber and Pipewire? I'm not even sure if both need to be aware of it.

[hcsch]

You're totally right. I think I just got a bit confused about what requires what to work when I wrote this. I was getting some errors in wireplumber about not being able to find the lv2 plugins, or something along those lines, but all docs (that I found) described this as a feature of pipewire, not wireplumber. And I kinda remember getting some errors from pipewire too, but that might've been due to other issue earlier when I was writing these changes, when I was having some other issues as well.
Anyways, I've taken out the LV2 config options / environment variables from the pipewire module and tested the setup again on my nixos (with nixpkgs at nixos-unstable) and it seemed to worked just fine.

[K900]

Overall looks pretty good

[K900]

OK let's send it.