made impermanence config work slightly better

modules/nixos-modules/ssh.nix

@@ -1,13 +1,28 @@
-{...}: {
-  services = {
-    openssh = {
-      enable = true;
-      ports = [22];
-      settings = {
-        PasswordAuthentication = false;
-        UseDns = true;
-        X11Forwarding = false;
+{
+  lib,
+  config,
+  ...
+}: {
+  config = lib.mkMerge [
+    {
+      services = {
+        openssh = {
+          enable = true;
+          ports = [22];
+          settings = {
+            PasswordAuthentication = false;
+            UseDns = true;
+            X11Forwarding = false;
+          };
+        };
       };
-    };
-  };
+    }
+    (lib.mkIf config.host.impermanence.enable {
+      environment.persistence."/persist/system/root" = {
+        directories = [
+          "/etc/ssh"
+        ];
+      };
+    })
+  ];
 }