Function handle_protected_resource_metadata 

pub(crate) async fn handle_protected_resource_metadata(
    __arg0: Extension<Shared<Receiver<Client>>>,
    __arg1: Extension<McpOAuthConfig>,
    __arg2: Extension<OauthMetadataMetrics>,
    req: Request,
) -> Response

HTTP handler for PROTECTED_RESOURCE_METADATA_PATH.

Always public: no authentication is performed, by design. RFC 9728 places no auth requirements on this endpoint; clients must be able to fetch it before they have a token.

Returns 404 when this listener does not advertise OAuth (see McpOAuthDiscovery) or has no issuer configured, 503 if the adapter client is not yet available (a brief window at startup), 400 if the request has no host information to construct a URL with, and 200 with the JSON document otherwise.