Add nonce endpoint issuer metadata (#27)

* Add nonce endpoint issuer metadata

* Editorial update

Co-authored-by: Giuseppe De Marco <giuseppe.demarco@teamdigitale.governo.it>

* Editorial update

Co-authored-by: Giuseppe De Marco <giuseppe.demarco@teamdigitale.governo.it>

* Edit the Nonce Issuer Metadata

the example is compliant with the OAuth 2.0 Authorization Server Metadata

---------

Co-authored-by: Giuseppe De Marco <giuseppe.demarco@teamdigitale.governo.it>

draft-demarco-oauth-nonce-endpoint.md

@@ -119,6 +119,25 @@ Below is an example of how an OAuth 2.0 Authorization Server Metadata might incl
 }
 ~~~~
 
+## Nonce Issuer Metadata
+
+The Nonce Issuers that uses the Nonce endpoint MUST include in their entity metadata the following parameter:
+
+ - **nonce_endpoint**: REQUIRED. This MUST be an HTTPS URL specifying the endpoint where clients can request a Nonce.
+
+Below a non-normative example of Nonce Issuer Metadata :
+
+~~~~
+{
+  "issuer": "https://walletprovider.example.com",
+  "authorization_endpoint": "https://walletprovider.example.com/authorize",
+  "response_types_supported": ["code", "token"]
+  "token_endpoint": "https://walletprovider.example.com/token",
+  "nonce_endpoint": "https://walletprovider.example.com/nonce",
+...
+}
+~~~~
+
 # Nonce Request
 
 When a Client needs a Nonce, it sends an HTTP GET request to the Nonce Endpoint.