log headers if 429 encountered

[whoabuddy]

This would've helped a lot diagnosing the last round of issues - 429 can mean we're hitting it too fast OR that we've hit a monthly quota, and the headers return more info about both.

If we just default to raising a logger.warn() every time we hit a 429 then the extra info will be easy to pinpoint right away.

[biwasxyz]

This repository has been retired and will be archived soon. The hosted agent infrastructure has been superseded. If this issue is still relevant, please open a new issue in the appropriate active repo.