add client error `Too_many_requests

[vbmithr]

No description provided.

[seliopou]

Which RFC does this come from? The one's explicitly mentioned in the Status module are the ones described in RFC7231§6.

[vbmithr]

https://tools.ietf.org/html/rfc6585

[sazarkin]

Maybe we should add all of them from rfc6585

• 428 Precondition Required
• 429 Too Many Requests
• 431 Request Header Fields Too Large
• 511 Network Authentication Required

[vbmithr]

@seliopou @sazarkin

What do you guys want to do with statuses from newer RFCs? Merge them, or just continue to use ``Code x`? I'm fine with both solutions, but please process those PRs either by closing them or merging them.

[somebody1234]

also worth noting that there's also rfc4918 - which has `Unprocessable_entity (#191) which is useful for requests that are syntactically well-formed (?) but semantically wrong

of course, it's worth noting that the official status of both are proposed standards so maybe they shouldn't be added - however it's also very unlikely that the same codes will be reused for a different purpose.

also MDN lists them, and httpaf already includes other non-rfc7231 status codes like `I_m_a_teapot