[NixOS] Set up agenix and auto import gpg key

nixos/secrets.nix

@@ -0,0 +1,21 @@
+{ inputs, pkgs, ... }: {
+  home-manager.users.imalison = ({ config, ... }: {
+    imports = [ inputs.agenix.homeManagerModules.default ];
+    age.identityPaths = [ "${config.home.homeDirectory}/.ssh/id_ed25519" ];
+    home.packages = [
+      inputs.agenix.packages."${pkgs.system}".default
+    ];
+    age.secrets.gpg-keys.file = ./secrets/gpg-keys.age;
+
+    systemd.user.services.import-gpg-key = {
+      Unit = {
+        Description = "Import GPG private key";
+      };
+      Install.WantedBy = [ "default.target" ];
+      Service = {
+        Type = "oneshot";
+        ExecStart = "${pkgs.gnupg}/bin/gpg --batch --import /run/user/%U/agenix/gpg-keys";
+      };
+    };
+  });
+}