CompletableFuture<OAuth2TokenDescriptor> introspect(String accessToken) {
        return introspect(accessToken, ACCESS_TOKEN);
    }
Implements Token introspection request/response flow, as per
<a href="https://datatracker.ietf.org/doc/html/rfc7662">RFC 7662</a>.
oauth2/src/main/java/com/linecorp/armeria/server/auth/oauth2/TokenIntrospection.java