Silent 400 error when headers exceed 8KiB

[cben]

Several people on our team have been plagued by a heisenbug — some requests sometimes start failing with status 400, no explanation and nothing logged 😕

Turns out we're hitting NodeJS limit of 8KiB headers (nodejs/node@1860352), when you accumulate too many cookies. 💡 A different tab / incognito might help because different cookies. Only some requests fail because they're longer...

• Workaround: clearing cookies helps!
• Can we return a clearer error (status 431 exists for this) and/or log a clear error? Looks like this can be caught in JS:
  https://github.com/nodejs/node/blob/87805375645f7af36fce2e59289559f746a7131d/doc/api/http.md#event-clienterror
• Can we set a higher limit!? Maybe: cli: add --max-http-header-size flag nodejs/node#24811

[cben]

• Workaround specific to OCM (cloud.redhat.com/openshift): append ?env=staging to browser URL to make OCM UI talk directly to stage API, bypassing insights-proxy.