Creates an encrypted cookie storage engine. Accepts the following options:
:key - The secret key to encrypt the session cookie. Must be a byte array of
 exactly 16 bytes. If no key is provided then a random key will be
 generated. Note that in that case a server restart will invalidate all
 existing session cookies.
:readers - A map of data readers used to read the serialized edn from the
 cookie. For writing, ensure that each data type has a key in the
 clojure.core/print-method or clojure.core/print-dup multimethods.