EDV Authorization with gnap

[rolsonquadras]

Currently, the client need to send ZCap authorization. This results in lots of calls to kms to sign zcap and then validate zcaps in ops-kms (zcaps are json-ld objects). The new design try to simply authorization model by using gnap protocol.

Ref - https://github.com/trustbloc/docs/blob/main/designs/auth.md