Nginx How to Extract a field from a JSON body response to an OAuth server?

I would like Nginx to call an External OAuth server to validate a bearer token and additionally extract the client_id from the OAuth validation response. I need the client_id to apply rate limiting.

However, I have not been able to find a native way in Nginx to simply extract an attribute from a response body. I was hoping to do something simple like regexing a variable such as $response_body.

I did see a couple of alternative options, such as installing a Luo module or a Javascript module.

Is there any way to do this natively in Nginx or do I have to use a custom option?

The response body from the OAuth server would look something like:

{
    "active": true,
    "client_id": "abc123"
}

I've gotten this far:

        location / {
            set $bearer_token "";
            if ($http_authorization ~* "^Bearer\s(.+)$") {
                set $bearer_token $1;
            }

            auth_request /oauth_validate;

            proxy_pass https://my-server;

            # I would like to extract the "active" and "client_id" values from the response body here
            # And then approve/disprove and apply rate limiting on the client_id
        }

        location /oauth_validate {
            internal;
            proxy_method POST;
            proxy_pass_request_headers off;
            proxy_set_header Content-Type "application/x-www-form-urlencoded";
            proxy_set_body "token=$bearer_token&client_credentials&client_id=foo&client_secret=bar";
            
            proxy_pass https://external-oauth.com/oauth2/default/v1/introspect;
        }