[rfc] Making HTTP::Cookie fully? comply with RFC 6265.

[bmmcginty]

Edited for correctness.
It is possible the below isn't needed, if we aren't trying to support Internet Explorer as a client to a Crystal server.

Looking at HTTP::cookie (in the latest Crystal revision), we aren't complying with RFC 6265 as regards max-age and expires.
See:
https://tools.ietf.org/html/rfc6265#section-4.1.2.2

https://tools.ietf.org/html/rfc6265#section-5.2.2

1. According to these, we should be noting a cookie as expired when the max-age header <=0 (assuming we aren't attempting to emulate Internet Explorer). This _is _done currently, but it discards the expires header.
2. We should be storing max-age as a separate value, and should be able to determine it's actual time based on the creation time of the cookie.
3. The max_age and expires values should both be modifiable so that exact cookies can be created as desired.

I've got a PR I'm working on to do the following:

1. add creation_time to each cookie, set to when #initialize is run.
2. change #expires to return the expires header value.
3. make max_age a Time::Span
4. generate string cookies using max-age and expires if they are defined.

Issues:

1. #expires now returns the expires value, not the actual expiration time (which can be dependent on max-age if provided). I don't have a suitable name to replace this method with. In other words, I need a method name for a method to give the calculated expiration time for a cookie.

Thoughts would be appreciated.

[asterite]

Maybe we can use expiration_time to return the Time. Other than that, your PR will be very welcome 👍

[watzon]

I was going to make a separate issue, but seeing as this is here already I'll just add to it. It seems as though Cookie#parse_set_cookie currently tries to set max_age to an Int32 which breaks with higher numbers. I attempted to parse a cookie earlier and got the following stack trace:

Unhandled exception: Invalid Int32: 9999999999 (ArgumentError)
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/string.cr:411:83 in 'to_i32'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/string.cr:322:5 in 'to_i'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/http/cookie.cr:104:32 in 'parse_set_cookie'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/http/cookie.cr:153:11 in 'fill_from_headers'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/http/cookie.cr:139:27 in 'from_headers'
  from lib/halite/src/halite/client.cr:268:7 in 'store_cookies_from_response'
  from lib/halite/src/halite/client.cr:262:7 in 'handle_response'
  from lib/halite/src/halite/client.cr:251:7 in 'handle_response'
  from lib/halite/src/halite/client.cr:153:7 in 'perform'
  from lib/halite/src/halite/client.cr:109:9 in '->'
  from lib/halite/src/halite/client.cr:255:3 in 'perform_chain'
  from lib/halite/src/halite/client.cr:108:7 in 'request'
  from lib/halite/src/halite/chainable.cr:447:7 in 'request:headers:params:raw:tls'
  from lib/halite/src/halite/chainable.cr:5:5 in 'get:headers'
  from src/arachnid/agent.cr:323:34 in 'visit_page'
  from src/arachnid/agent.cr:205:11 in 'run'
  from src/arachnid/agent.cr:176:14 in 'start_at'
  from src/arachnid/agent.cr:134:7 in 'start_at'
  from src/arachnid/arachnid.cr:27:5 in 'start_at'
  from src/arachnid.cr:7:1 in '__crystal_main'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/crystal/main.cr:97:5 in 'main_user_code'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/crystal/main.cr:86:7 in 'main'
  from /home/watzon/.asdf/installs/crystal/0.29.0/share/crystal/src/crystal/main.cr:106:3 in 'main'
  from __libc_start_main
  from _start
  from ???

[RX14]

@watzon this is a separate issue, please make a new issue or PR. Numbers greater than Int32::MAX can be truncated in practice, since recording values of more than 68 years in this field is unneccesary.

[watzon]

@RX14 I already opened a PR #7925 which should fix both issues