Off-board JP and promote Ben in production

Part of #163 (closed)

1. Off-board JP
2. Promote Ben ssh key to replace JP in production (and drop Ben's legacy key)

morph/grid/local/public-keys/users.nix.example

@@ -4,7 +4,7 @@ let
 # You can use the following to get key from the local machine.
 # key = builtins.readFile ~/.ssh/id_ed25519.pub;
   key = undefined;
-  keys = [key]
+  keys = [key];
 in {
   "root" = keys;
   "vagrant" = keys;