elixir: make 1.15 default and pin existing pkgs to 1.14

- `zfs` was updated from 2.1.x to 2.2.0, [enabling newer kernel support and adding new features](https://github.com/openzfs/zfs/releases/tag/zfs-2.2.0).

- Elixir now defaults to version

  [v1.15](https://elixir-lang.org/blog/2023/06/19/elixir-v1-15-0-released/).

- A new option was added to the virtualisation module that enables specifying explicitly named network interfaces in QEMU VMs. The existing `virtualisation.vlans` is still supported for cases where the name of the network interface is irrelevant.

- DocBook option documentation is no longer supported, all module documentation now uses markdown.

  # Erlang/Elixir uses a somewhat special format for IP addresses

  erlAddr = addr: fileContents

    (pkgs.runCommand addr {

      nativeBuildInputs = with pkgs; [ elixir ];

      nativeBuildInputs = [ cfg.package.elixirPackage ];

      code = ''

        case :inet.parse_address('${addr}') do

          {:ok, addr} -> IO.inspect addr

      passAsFile = [ "code" ];

    } ''elixir "$codePath" >"$out"'');

  format = pkgs.formats.elixirConf { };

  format = pkgs.formats.elixirConf { elixir = cfg.package.elixirPackage; };

  configFile = format.generate "config.exs"

    (replaceSec

      (attrsets.updateManyAttrsByPath [{

  initSecretsScript = writeShell {

    name = "akkoma-init-secrets";

    runtimeInputs = with pkgs; [ coreutils elixir ];

    runtimeInputs = with pkgs; [ coreutils cfg.package.elixirPackage ];

    text = let

      key-base = web.secret_key_base;

      jwt-signer = ex.":joken".":default_signer";

  user = "mobilizon";

  group = "mobilizon";

  settingsFormat = pkgs.formats.elixirConf { elixir = pkgs.elixir_1_14; };

  settingsFormat = pkgs.formats.elixirConf { elixir = cfg.package.elixirPackage; };

  configFile = settingsFormat.generate "mobilizon-config.exs" cfg.settings;

          genCookie = "IO.puts(Base.encode32(:crypto.strong_rand_bytes(32)))";

          evalElixir = str: ''

            ${pkgs.elixir_1_14}/bin/elixir --eval '${str}'

            ${cfg.package.elixirPackage}/bin/elixir --eval '${str}'

          '';

        in

        ''

      elvis-erlang = callPackage ./elvis-erlang { };

      # BEAM-based languages.

      elixir = elixir_1_14;

      elixir = elixir_1_15;

      elixir_1_15 = lib'.callElixir ../interpreters/elixir/1.15.nix {

        inherit erlang;

  passthru = {

    tests = with nixosTests; { inherit akkoma akkoma-confined; };

    inherit mixNixDeps;

    # Used to make sure the service uses the same version of elixir as

    # the package

    elixirPackage = beamPackages.elixir;

  };

  meta = with lib; {