Cloudflare does not cache responses with Set-Cookie by default, and phorge greets new connections with Set-Cookie probably for CSRF stuff.

• Cloudflare does not cache the resource when:
  • The Cache-Control header is set to private, no-store, no-cache, or max-age=0.
  • The Set-Cookie header exists.

For robots.txt, I don't think we need it and we should just let it cache by not setting cookies.

For now we can demand Cloudflare to detach the cookies, but it is desirable to un-set the cookie at phorge level.