feat(nixos): add user password secrets to sops

This commit adds the user password secrets to sops.
It leverages the `userListToAttrs` lib function.

nix/flake-parts/meta.nix

@@ -18,17 +18,22 @@ in
       type = lazyAttrsOf raw;
       default = { };
     };
-    root = mkOption {
-      type = path;
-      default = "";
+    paths = {
+      root = mkOption { type = path; };
+      secrets = mkOption {
+        type = path;
+        readOnly = true;
+      };
     };
     admin = mkOption {
       type = lazyAttrsOf raw;
       default = { };
     };
   };
-
-  config.flake.admin = cfg.manifest.users.${username} // {
-    inherit username;
+  config.flake = {
+    paths.secrets = cfg.paths.root + "/secrets";
+    admin = cfg.manifest.users.${username} // {
+      inherit username;
+    };
   };
 }

nix/modules/secrets.nix

@@ -16,12 +16,9 @@ in
     { config, ... }:
     {
       imports = [ inputs.sops-nix.nixosModules.sops ];
-      config.sops = {
-        defaultSopsFile = "${cfg.root}/secrets/secrets.yaml";
-        age.sshKeyPaths = [
-          "/persist${config.users.defaultUserHome}/${username}/.ssh/id_ed25519"
-        ];
-      };
+      config.sops.age.sshKeyPaths = [
+        "/persist${config.users.defaultUserHome}/${username}/.ssh/id_ed25519"
+      ];
     };
   perSystem =
     { pkgs, ... }:

nix/modules/users.nix

@@ -1,7 +1,7 @@
 { config, lib, ... }:
 let
   cfg = config.flake;
-  inherit (cfg.lib.modules) forAllUsers';
+  inherit (cfg.lib.modules) userListToAttrs forAllUsers';
   inherit (lib.lists) optional;
 in
 {
@@ -19,13 +19,20 @@ in
         mutableUsers = false;
         groups.users.gid = 100;
         users = forAllUsers' (
-          _: value: {
+          name: value: {
             isNormalUser = true;
+            hashedPasswordFile = config.sops.secrets."${name}/hashedPassword".path;
             extraGroups = optional (value.primary or false) "wheel";
             openssh.authorizedKeys.keys = [ value.pubkey ];
           }
         );
       };
+      sops.secrets = userListToAttrs (name: {
+        "${name}/hashedPassword" = {
+          neededForUsers = true;
+          sopsFile = cfg.paths.secrets + "/users.yaml";
+        };
+      });
       home-manager.users = forAllUsers' (
         name: _: {
           home.username = name;