persistent directory for luks keys

nixos/common.nix

@@ -300,7 +300,7 @@
         "/etc/ssh/user_ca.pub"
       ];
     };
-
+    "/mnt/data" = { directories = [ "/etc/luks-keys" ]; };
     "/mnt/logs" = { directories = [ "/var/log" ]; };
   };