Add package 'mailnix' for assisting in generation of dovecot/postfix files

flake.nix

@@ -7,6 +7,7 @@
     flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
     treefmt-nix.url = "github:numtide/treefmt-nix";
     treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
+    crane.url = "github:ipetkov/crane";
     git-hooks-nix.url = "github:cachix/git-hooks.nix";
     git-hooks-nix.inputs.nixpkgs.follows = "nixpkgs";
   };
@@ -23,6 +24,7 @@
         "aarch64-linux"
       ];
       imports = [
+        flake-parts.flakeModules.easyOverlay
         inputs.treefmt-nix.flakeModule
         inputs.git-hooks-nix.flakeModule
       ];
@@ -34,7 +36,10 @@
         pkgs,
         system,
         ...
-      }: {
+      }: let
+        craneLib = inputs.crane.mkLib pkgs;
+        pkgs = nixpkgs.legacyPackages.${system}.extend self.overlays.default;
+      in {
         checks = let
           tests = ["internal" "basic" "aliases" "rspamd"];
           genTest = testName: {
@@ -44,9 +49,20 @@
         in
           pkgs.lib.listToAttrs (map genTest tests);
 
-        devShells.default = pkgs.mkShell {
+        packages = rec {
+          default = mailnix;
+          mailnix = craneLib.buildPackage {
+            src = craneLib.cleanCargoSource ./pkgs/mailnix;
+          };
+        };
+        overlayAttrs = {
+          mailnix = config.packages.mailnix;
+        };
+
+        devShells.default = craneLib.devShell {
           packages = with pkgs; [
             self'.formatter.outPath # Add all formatters to environment
+            mailnix
           ];
           shellHook = ''
             ${config.pre-commit.installationScript}
@@ -61,6 +77,7 @@
           programs = {
             actionlint.enable = true;
             alejandra.enable = true;
+            rustfmt.enable = true;
           };
           settings.global.excludes = [
             ".envrc"