[REQ][javascript] Ability to intercept requests and dynamically compute an authorization header value

Hi,

Is your feature request related to a problem? Please describe.

I generated a client library using openapi-generator-cli and the following command:

java -jar openapi-generator-cli.jar generate -i *.yaml -g javascript -o out

I'm now searching for a way to inject an OAuth header computed from the request without changing the generated code.

Describe the solution you'd like

The ability to pass superagent request interceptors or "authenticators" to the ApiClient instance.

Describe alternatives you've considered

I tried the following:

1. Override applyAuthToRequest to set the header

client.applyAuthToRequest = function(request) {
    const auth = computeAuthorization(request);
    request.set({'Authorization': auth });
  };

But applyAuthToRequest is called too early, when the request object is not entirely filled.

2. Override applyAuthToRequest to add a listener to requests

client.applyAuthToRequest = function(request) {
    request.addListener("end", function() {
        // ...
    });
  };

But the end event seems to be the only event we can listen to, and it happens to late.

3. Pass a custom requestAgent to the ApiClient

const apiClient = require('../../ApiClient.js');
const requestAgent = new require("https").Agent({ /* Options */});
const client = apiClient.instance;
client.requestAgent = requestAgent; 
(...)

In that case the custom agent is used, but I haven't find any way of adding interceptors or listening to requests.

Any help would be appreciated.