[mcp] Adds back the user changes I accidentally clobbered.

system/hosts/mcp/containers/offen.nix

@@ -1,10 +1,7 @@
 { config, ... }:
 let
   inherit (import ./lib.nix config) mkContainer terakoda;
-  userIds = import ./user-ids.nix;
 in {
-  users = userIds.mkUserAndGroup "offen" userIds.offen;
-
   sops = {
     secrets = {
       "offen/smtp-token" = {};
@@ -30,7 +27,7 @@ in {
     image = "offen/offen";
     hostName = "offen";
     domain = terakoda;
-    user = "${toString userIds.offen.uid}:${toString userIds.offen.gid}";
+    user = "${toString config.users.users.offen.uid}:${toString config.users.groups.offen.gid}";
     port = 80;
     volumes = [
       "${config.sops.templates."offen.env".path}:/etc/offen/offen.env:ro"