Allow users to override cache control headers

[charliermarsh]

Some registries don't provide any cache-control headers, which can make for a suboptimal experience (see: #10359). (PyPI returns 10-minute caching headers.) I wonder if it makes sense to allow users to override the cache-control headers?

[zanieb]

See also #10380

[charliermarsh]

#10380 seems different -- that appears to be a request that we add a mode that attempts to hit the index, but falls back to --offline behavior if it's unavailable?

[zanieb]

I agree it's different. I think the similarity is that we may need to override cache control headers (as I mentioned there) to read from a stale cache? I'm not actually familiar with how that interacts with the offline mode.

[charliermarsh]

I believe we allow reading from a stale cache in offline mode.