Add 'retryAfter' property to 'Too Many Request' Error

This is a number in the Retry-After header, when the statuscode is 429.

[kauffecup]

This PR https://github.com/thelinmichael/spotify-web-api-node/pull/237 adds the entire headers object to the error, so consumers can take advantage of the retry-after header. For example, could do something like:

  const doRequest = async (args, retries) => {
    try {
      const response = await spotifyApi.getMySavedTracks(args);
      return response;
    } catch (e) {
      if (retries > 0) {
        console.error(e);
        await asyncTimeout(
          e.headers['retry-after'] ?
            parseInt(e.headers['retry-after']) * 1000 :
            RETRY_INTERVAL
        );
        return doRequest(args, retries - 1);
      }
      throw e;
    }
  };

This creates a wrapper around the request and retries it if the request fails

[jopek]

@gwynnebaer if i see correctly, using superagent-throttle only allows you to throttle all requests, rather than using the Retry-After header.

@settheset chose to at first automatically retry bases on the Retry-After header but reverted it back to passing the headers to the error object. https://github.com/thelinmichael/spotify-web-api-node/blob/master/src/http-manager.js#L88

Passing the header along with the error object allows one to make use of RxJs’ retryWhen operator and supplying the delay operator the Retry-After value.