nixos/pipewire: add assertions for migration to extraConfig/configPackages

[hcsch]

Description of changes

The PR #282377 made files/directories specified in environment.etc."pipewire<...>" and environment.etc."wireplumber<...>" conflict with existing configuration of the PipeWire NixOS module due to how the configPackages options were implemented. This sadly wasn't easily avoidable. As this can cause breakage for users moving from 23.11 to 24.05 though, assertions can help guide them to use services.pipewire.extraConfig or services.pipewire.configPackages / services.wireplumber.configPackages instead, fixing the breakage.

Wireplumber probably still needs an additional extraConfig and extraScrips (or extraPolicies, extraScripts; open for bikeshedding) options.

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.

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[tpwrules]

Need to look more carefully, but "deprecated" should be replaced by "removed". If the old ones don't work and it's an assert failure to use them it's not a deprecation.

[NotAShelf]

I don't understand the decision to force an user to package WirePlumber rules to be able to write a few rules for WP. Is there a reason why this assertion was thrown in, but not an extraConfig option?

[hcsch]

This assertion PR was just a quick fix. I'm afraid the main PR was just not ready yet in hindsight. I'll work on a follow-up for an extraConfig option for wireplumber today to get that fixed

[leonm1]

Is it possible to add this to the backwards incompatible changes section in the release notes?

I ran into this issue and checked the release notes, but I was unable to figure out how to use the new option, since man configuration.nix did not contain the referenced option (yet), since I wasn't able to build a nixos configuration containing that option 😅

I did find this commit, which would help others experiencing the same.

[hcsch]

@leonm1 created #293248 to document this breaking change in the release notes of 24.05. Thanks for bringing the release notes to my attention