Mints a zcap capability carrying a token model, signed by the AS.
the token model gnap_access validates
gnap_access
{ cryptosuite, privateKey, controller, keyId }, plus publicJwk for a JCS suite
{ cryptosuite, privateKey, controller, keyId }
publicJwk
{ value, format, jti }, or a refusal
{ value, format, jti }
Mints a zcap capability carrying a token model, signed by the AS.