Manage CDN cache TTL from proxito

[stsewd]

Currently we are using CloudFlare's default, which isn't really explicit about the default value... but looks like it's 1 or 2 hours.

We already control caching level using the CDN-Cache-Control header (private vs public), that same header accepts the max-age directive to indicate the TTL for the edge cache

readthedocs.org/readthedocs/proxito/middleware.py

Line 171 in 9d1e0b1

header = "CDN-Cache-Control"

https://developers.cloudflare.com/cache/about/cdn-cache-control

User feedback

We also had a user who wanted the ability to set different TTL's for files based on version:

Just ran across this issue, and thanks for dropping the TTL. I got bit by this because we serve JSON resources on our site and Deno respects the Cache-Control max-age when loading Javascript or JSON documents from the internet. Days or even months is fine for our versioned docs, as we will almost never rebuild, but /en/latest/ is useful to have on the order of 5-30 minutes.

Could be interested as an advanced user feature, or just something we set in the admin via support 🤔

This is similar to what we do with sitemaps: https://docs.readthedocs.io/en/stable/reference/sitemaps.html#how-it-works

[ericholscher]

We also talked about more aggressively caching fonts and static files, since they generally have hashes. Also they don't really change too frequently, so a missed cache invalidation isn't a huge deal.

[ericholscher]

readthedocs.org/readthedocs/proxito/middleware.py

Line 171 in 9d1e0b1

header = "CDN-Cache-Control"

This should probably be cache_header = :)

[stsewd]

Some ideas of how to make this configurable per view #10067 (comment)