jsonWebKeySetUrl

RFC 7800: The proof-of-possession key can be passed by reference instead of being passed by value. This is done using the "jku" member. Its value is a URI (RFC3986) that refers to a resource for a set of JSON- encoded public keys represented as a JsonWebKeySet, one of which is the proof-of-possession key. If there are multiple keys in the referenced JWK Set document, a keyId member MUST also be included with the referenced key's JWK also containing the same keyId value.