New endpoint for nonce for OIDC4VCI draft 14

[ThierryThevenet]

need before #3180

For OIDC4VCI draft > =14, the token endpoint does not return a c_nonce. So wallet MUST get the nonce for the key proof of ownership jwt from a new nonce endpoint provided by the issuer. This nonce is used to provide the jwt or ldp_vp proof in the credential request

To get the nonce

1. get the nonce endpoint URL from the credential issuer metadata : nonce_endpoint:
2. make a POST to this endpoint

Example:

POST /issuer/nonce HTTP/1.1
Host: talao.co
Content-Length: 0

Response from issuer should be :

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store

{
  "c_nonce": "wKI4LT17ac15ES9bw8ac4"
}

3. use the c_nonce to build the proof of key ownership

If nonce endpoint is not available than raise an error message 'invalid_response' with error_description 'Nonce endpoint is not available'

[ThierryThevenet]

You can test it on all OIDC4VCI draft 13 test with the wallet setup with draft 14.