Serialize the RFC 8414 AS metadata document the proxy serves at
/.well-known/oauth-authorization-server. Emits the proxy endpoints,
response_types_supported (RFC 8414 §2 REQUIRED when
authorization_endpoint is present), code_challenge_methods_supported,
grant_types_supported, token_endpoint_auth_methods_supported, and
(when non-empty) scopes_supported.
Serialize the RFC 8414 AS metadata document the proxy serves at /.well-known/oauth-authorization-server. Emits the proxy endpoints, response_types_supported (RFC 8414 §2 REQUIRED when authorization_endpoint is present), code_challenge_methods_supported, grant_types_supported, token_endpoint_auth_methods_supported, and (when non-empty) scopes_supported.