broke out certDir for home manager module

modules/hosts/john-pc-ubuntu.nix

@@ -8,11 +8,9 @@ in
   flake.modules.homeManager."${hostname}" = { pkgs, config, ... }:
   let
     flakeDir = "${config.xdg.configHome}/home-manager/jsl-dendritic";
-    certDir = "${config.home.homeDirectory}/.step/certs";
+    certDir = "${config.mtls.certDir}";
     CACert = "${certDir}/root_ca.crt";
-    tlsKey = "${certDir}/key.pem";
-    tlsCert = "${certDir}/cert.pem";
-    mtlsCert = "${certDir}/mtls.pem";
+    mtlsBundle = "${certDir}/${config.mtls.bundleFilename}";
   in
   {
     imports = with inputs.self.modules.homeManager; [
@@ -41,9 +39,9 @@ in
 
     mtls = {
       enable = true;
-      subject = hostname;
       caURL = "https://janus.john-stream.com/";
       provisioner = "admin";
+      subject = hostname;
       san = [
         "${hostname}"
         "192.168.1.85"
@@ -87,7 +85,7 @@ in
           "inherit" = "base";
           repository = "rest:https://soteria.john-stream.com/john-ubuntu";
           cacert = "${CACert}";
-          tls-client-cert = "${mtlsCert}";
+          tls-client-cert = "${mtlsBundle}";
           backup = {
             source = [
               "${config.xdg.userDirs.documents}"