proteus New Prekey
Creates a new Proteus prekey with the given ID and returns its CBOR-serialized bundle.
Fails if the ID is already in use. Prekeys are not replaceable: the ID has been published to peers in a bundle, and overwriting it would strand anyone still holding that bundle. Use proteus_new_prekey_auto to have a free ID chosen instead.
Warning: the Proteus client must be initialized with proteus_init first or an error will be returned.