nixos: create 'modules/nixos' folder

Let's consolidate all modules under one path, so that NixOS,
home-manager, and nix-darwin (if I ever end up using it down the line)
would go under the same folder.

modules/nixos/system/users/default.nix

@@ -0,0 +1,51 @@
+# User setup
+{ config, lib, pkgs, ... }:
+let
+  secrets = config.age.secrets;
+  cfg = config.my.system.users;
+  groupExists = grp: builtins.hasAttr grp config.users.groups;
+  groupsIfExist = builtins.filter groupExists;
+in
+{
+  options.my.system.users = with lib; {
+    enable = my.mkDisableOption "user configuration";
+  };
+
+  config = lib.mkIf cfg.enable {
+    users = {
+      mutableUsers = false; # I want it to be declarative.
+
+      users = {
+        root = {
+          hashedPasswordFile = secrets."users/root/hashed-password".path;
+        };
+
+        ${config.my.user.name} = {
+          hashedPasswordFile = secrets."users/ambroisie/hashed-password".path;
+          description = "Bruno BELANYI";
+          isNormalUser = true;
+          shell = pkgs.zsh;
+          extraGroups = groupsIfExist [
+            "audio" # sound control
+            "docker" # usage of `docker` socket
+            "media" # access to media files
+            "networkmanager" # wireless configuration
+            "plugdev" # usage of ZSA keyboard tools
+            "podman" # usage of `podman` socket
+            "video" # screen control
+            "wheel" # `sudo` for the user.
+          ];
+          openssh.authorizedKeys.keys = with builtins;
+            let
+              keyDir = ./ssh;
+              contents = readDir keyDir;
+              names = attrNames contents;
+              files = filter (name: contents.${name} == "regular") names;
+              keys = map (basename: readFile (keyDir + "/${basename}")) files;
+            in
+            keys;
+        };
+      };
+    };
+  };
+}

modules/nixos/system/users/ssh/aramis.pub

@@ -0,0 +1 @@
+ssh-rsa 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 ambroisie@aramis

modules/nixos/system/users/ssh/shared.pub

@@ -0,0 +1 @@
+ssh-rsa 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 ambroisie@shared-key