Desired behaviour: in general, our caches (Cloudflare, nginx) should cache things briefly (1 day? 6 hours?), while the user's browser should cache things longer (1 week? month?). (We can set different cache times by using both max-age and s-maxage.) This reduces the time it takes for archive updates to reach the user (#64).

Specifics:

• Should be cached in Cloudflare briefly and in the browser for a ~week
  • Index pages
  • Regular files on main domain
  • Unsafe files on subdomains
  • Error pages (except maybe for zip file not found errors? Should they be cached shorter?)
  • Redirects of regular files from subdomain to main domain (shouldn't be forever just in case we have to handle more Unity games that need to be all the same domain, etc)
• Should be cached forever
  • Redirects to unsafe HTML files
  • Files with ?lastmod

We could consider doing more ?lastmod stuff, such as automatically adding it to the links in index pages. But it's not really needed, and it's a detail I think would be better to hide from the user. (Using it for HTML game redirects is more hidden.)