Also expose OAuth AS metadata at .well-known/oauth-authorization-server

Github Issue Link: Also expose OAuth AS metadata at .well-known/oauth-authorization-server by Splashing23 - Pull Request #138 - xwiki-contrib/oidc

Summary

• Register the existing OIDC discovery handler for .well-known/oauth-authorization-server in addition to .well-known/openid-configuration.
• Lets MCP/OAuth clients that follow RFC 8414 discover XWiki's authorization/token/registration endpoints instead of falling back to guessing /authorize on the host root.

Context

XWiki already returns correct OpenID Connect Discovery JSON at /oidc/.well-known/openid-configuration. MCP clients (and similar OAuth resource clients) often request /oidc/.well-known/oauth-authorization-server first per RFC 8414. That path currently 404s, which breaks discovery even when Protected Resource Metadata correctly points at the /oidc issuer.

Test plan

•  GET /oidc/.well-known/oauth-authorization-server returns 200 with the same metadata JSON as openid-configuration
•  GET /oidc/.well-known/openid-configuration still returns 200 unchanged
•  Confirm authorization_endpoint, token_endpoint, issuer, and registration_endpoint are present