[OID4VP] Verifier endpoint to manage the AuthorizationRequestObject

### Proposed feature

This issue is a subtask of the https://github.com/hyperledger/identus/issues/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](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html#name-passing-authorization-reque).

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](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html#response_mode_post)) in conjunction with request_uri is RECOMMENDED, since Authorization Request size might be large and might not fit in a QR code.