At the point of doing this ticket, the secure version of the key ring insertion logic should already be laid down, and the '–extensionsSignaturePubKeyPath' server option should already exist in insecure build mode.

In this ticket, modify the key ring insertion logic to take an argument of which public key to insert. If the '–extensionsSignaturePubKeyPath' option is specified, the key in that path should be the one inserted into the key ring (otherwise, it should remain the production mongot-extensions.pub key).

Ensure that any logic that references '–extensionsSignaturePubKeyPath' is guarded under #ifndef MONGO_CONFIG_EXT_SIG_SECURE.