Update request.js

[dtadevos]

Hi,

For private_key_jwt authentication, our Provider, running behind the proxy, tries to retrieve the JWKS keys by the specified jwksUri configured endpoint.

We pass the proxy agent through httpOptions, as described in the configuration, e.g.:

httpOptions(urlstr) {
  const options = url.parse('http://proxy-fr-croissy.gemalto.com:8080');
  const agent = new HttpsProxyAgent(options);
  return {
    agent,
    timeout: 5000,
  };
},

That unfortunatelly didn't work, and the debug undentified 3 issues:

1. const helperOptions = omitBy({ timeout, agent, lookup }, Boolean);
   this code omits whatever is provided in httpOptions, so we had to change it to pickBy instead

2. if (!(agent instanceof HttpsAgent) && !(agent instanceof HttpAgent))
   this condition is not satisfied when I pass an instance of HttpsProxyAgent from 'https-proxy-agent', as it extends the Agent from 'agent-base' package. So we had to update the condition.

3. url: new URL(options.url)
   helperOptions.agent = { [options.url.protocol]: helperOptions.agent };
   options.url.protocol string is 'https:', but as the trailing extra column is causing a problem, we had to slice it.