refactor(nix): use flake-parts and flake-compat

- redefine `{default,shell}.nix` to derive from `flake.nix` (using
  `flake-compat`)
- use `flake-parts`' `_module.args.pkgs` machinery to apply overlays
  (instead of `pkgsFor`)
- extract `homeManagerModule` to `nix/module.nix`
- rename package at `nix/default.nix` to `nix/package.nix`

Co-authored-by: reo101 <pavel.atanasov2001@gmail.com>

nix/default.nix

@@ -1,144 +0,0 @@
-{
-  gtk3,
-  gdk-pixbuf,
-  librsvg,
-  webp-pixbuf-loader,
-  gobject-introspection,
-  glib-networking,
-  glib,
-  shared-mime-info,
-  gsettings-desktop-schemas,
-  wrapGAppsHook,
-  gtk-layer-shell,
-  gnome,
-  libxkbcommon,
-  libdbusmenu-gtk3,
-  libpulseaudio,
-  libinput,
-  libevdev,
-  openssl,
-  luajit,
-  luajitPackages,
-  pkg-config,
-  installShellFiles,
-  adwaita-icon-theme,
-  hicolor-icon-theme,
-  rustPlatform,
-  lib,
-  version ? "git",
-  features ? [],
-  builderName ? "nix",
-  builder ? {},
-}: let
-  hasFeature = f: features == [ ] || builtins.elem f features;
-
-  basePkg = rec {
-    inherit version;
-
-    pname = "ironbar";
-
-    src = builtins.path {
-      name = "ironbar";
-      path = lib.cleanSource ../.;
-    };
-
-    nativeBuildInputs = [
-        pkg-config
-        wrapGAppsHook
-        gobject-introspection
-        installShellFiles
-    ];
-
-    buildInputs = [
-      gtk3
-      gdk-pixbuf
-      glib
-      gtk-layer-shell
-      glib-networking
-      shared-mime-info
-      adwaita-icon-theme
-      hicolor-icon-theme
-      gsettings-desktop-schemas
-      libxkbcommon ]
-      ++ lib.optionals (hasFeature "http") [ openssl ]
-      ++ lib.optionals (hasFeature "tray") [ libdbusmenu-gtk3 ]
-      ++ lib.optionals (hasFeature "volume")[ libpulseaudio ]
-      ++ lib.optionals (hasFeature "cairo") [ luajit ]
-      ++ lib.optionals (hasFeature "keyboard") [ libinput libevdev ];
-
-    propagatedBuildInputs = [ gtk3 ];
-
-    lgi = luajitPackages.lgi;
-
-    gappsWrapperArgs = ''
-        # Thumbnailers
-            --prefix XDG_DATA_DIRS : "${gdk-pixbuf}/share"
-            --prefix XDG_DATA_DIRS : "${librsvg}/share"
-            --prefix XDG_DATA_DIRS : "${webp-pixbuf-loader}/share"
-            --prefix XDG_DATA_DIRS : "${shared-mime-info}/share"
-
-            # gtk-launch
-            --suffix PATH : "${lib.makeBinPath [ gtk3 ]}"
-    ''
-    + lib.optionalString (hasFeature "cairo") ''
-        --prefix LUA_PATH : "./?.lua;${lgi}/share/lua/5.1/?.lua;${lgi}/share/lua/5.1/?/init.lua;${luajit}/share/lua/5.1/\?.lua;${luajit}/share/lua/5.1/?/init.lua"
-        --prefix LUA_CPATH : "./?.so;${lgi}/lib/lua/5.1/?.so;${luajit}/lib/lua/5.1/?.so;${luajit}/lib/lua/5.1/loadall.so"
-    '';
-
-    preFixup = ''
-      gappsWrapperArgs+=(
-        ${gappsWrapperArgs}
-      )
-    '';
-
-    postInstall = ''
-      installShellCompletion --cmd ironbar \
-        --bash target/completions/ironbar.bash \
-        --fish target/completions/ironbar.fish \
-        --zsh target/completions/_ironbar
-    '';
-
-    passthru = {
-      updateScript = gnome.updateScript {
-        packageName = pname;
-        attrPath = "gnome.${pname}";
-      };
-    };
-
-    meta = with lib; {
-      homepage = "https://github.com/JakeStanger/ironbar";
-      description =
-        "Customisable gtk-layer-shell wlroots/sway bar written in rust.";
-      license = licenses.mit;
-      platforms = platforms.linux;
-      mainProgram = "ironbar";
-    };
-
-  };
-
-  flags = let
-    noDefault = if features == [ ] then "" else "--no-default-features";
-
-    featuresStr = if features == [ ] then
-      ""
-    else
-      ''-F "${builtins.concatStringsSep "," features}"'';
-
-  in [ noDefault featuresStr ];
-in if builderName == "naersk" then
-  builder.buildPackage (basePkg // { cargoBuildOptions = old: old ++ flags; })
-else if builderName == "crane" then
-  builder.buildPackage (basePkg // {
-    cargoExtraArgs = builtins.concatStringsSep " " flags;
-    doCheck = false;
-  })
-else
-  rustPlatform.buildRustPackage (basePkg // {
-    buildNoDefaultFeatures = features != [ ];
-
-    buildFeatures = features;
-    cargoDeps = rustPlatform.importCargoLock { lockFile = ../Cargo.lock; };
-    cargoLock.lockFile = ../Cargo.lock;
-    cargoLock.outputHashes."stray-0.1.3" =
-      "sha256-7mvsWZFmPWti9AiX67h6ZlWiVVRZRWIxq3pVaviOUtc=";
-  })