stalwart: add stalwart user

modules/services/stalwart/module.nix

@@ -13,6 +13,15 @@
 in {
   options.modules.system.services.stalwart.enable = mkEnableOption "stalwart";
   config = mkIf cfg.enable {
+    # create the stallwart user
+    users.users.stalwart = {
+      home = "/var/lib/stalwart-mail";
+      useDefaultShell = true;
+      group = "stalwart";
+      isSystemUser = true;
+    };
+    users.groups.stalwart = {};
+
     services.stalwart-mail = {
       enable = true;
       package = pkgs.stalwart-mail;
@@ -91,7 +100,7 @@ in {
           };
         };
         store = {
-          "postgresql" = {
+          postgresql = {
             # Specifies the database type, set to "postgresql" for PostgreSQL.
             type = "postgresql";
 
@@ -102,11 +111,15 @@ in {
             port = "5432";
 
             # Name of the database to connect to.
+            # TODO: add this to PostgreSQL.
             database = "stalwart";
 
             # The username used for authentication with the PostgreSQL server.
+            # TODO: add this to PostgreSQL.
             user = "stalwart";
 
+            password = "";
+
             # Enable TLS
             tls.enable = true;
           };