[OID4VP] Verifier endpoint to manage the AuthorizationRequestObject

[yshyn-iohk]

Proposed feature

This issue is a subtask of the hyperledger/identus#16

When using Cross-Device Flow and direct_post response mode, it is recommended to use Authorization Request Object. See Passing Authorization Request Across Devices.

The Cloud Agent, as a verifier, should support this endpoint.

Feature description

There are use-cases when the Authorization Request is being displayed on a device different from a device on which the requested Credential is stored. In those cases, an Authorization Request can be passed across devices by being rendered as a QR Code.

The usage of the Response Mode direct_post (see Section 6.2) in conjunction with request_uri is RECOMMENDED, since Authorization Request size might be large and might not fit in a QR code.