properly inherit enable on servers

modules/servers/postgres.nix

@@ -5,6 +5,7 @@
   ...
 }:
 let
+  cfg = config.my.servers.postgres;
   # upgrade here first, then below.
   upgrade-pg-cluster =
     let
@@ -42,10 +43,10 @@ let
 in
 {
   options.my.servers.postgres.enable = lib.mkEnableOption "enable";
-  config = lib.mkIf config.my.servers.postgres.enable {
+  config = lib.mkIf cfg.enable {
     environment.systemPackages = [ upgrade-pg-cluster ];
     services.postgresql = {
-      enable = true;
+      inherit (cfg) enable;
       enableTCPIP = true;
       ensureDatabases = dbNames;
       package = pkgs.postgresql_17;