Support setting payload_location(260) with indirect-sign/COSE Hash Envelope

[achamayou]

COSE Hash Envelope specifies an optional payload_location header parameter (260) defined in https://www.ietf.org/archive/id/draft-ietf-cose-hash-envelope-10.html#section-3, which can be used to give the location of the content whose digest is the payload of a COSE Hash Envelope.

It would be nice to be able to set in the API and on the CLI.