Test for new routes/query parameters that aren't in caching whitelist

[brainwane]

We ran into a VCL issue when deploying the new WebAuthn feature #5795. That's because: in dev, there's no caching layer, so if a new PR introduces a route that takes query parameters, it works locally, but in prod, if new routes are added, and if they have query parameters, and they're not in the caching whitelist (in https://github.com/python/pypi-infra ), things will break.

Should we add a CI test and fail the build? signal the problem as part of the deploy pipeline script?

(idea by @woodruffw)