Handle DPoP nonce returned from Nonce Endpoint

[dtsiflit]

OpenID4VCI draft 16 has introduced the following change in Nonce Endpoint:

The Credential Issuer MAY provide a DPoP nonce as an HTTP header as defined in Section 8.2 of [[RFC9449](https://openid.net/specs/openid-4- verifiable-credential-issuance-1_0-16.html#RFC9449)]). In this case, the Wallet uses the new nonce value in the DPoP proof when presenting an access token at the Credential Endpoint

• Update NonceEndpointClient to handle DPoP nonce response header if provided
• When creating proofs for the credential request pass the latest DPoP nonce returned from nonce endpoint to credential request