Bug with some proxies when using reqwest (reqwest is based on http underhood)

[chirok11]

Hello.
I have reached some HTTP proxies with authorization, which require http header names written as it's written in RFC.
when I am sending request by netcat

`GET http://site/ HTTP/1.1
proxy-authorization: Basic abcdef==
User-Agent: curl/7.79.1
Accept: /
Proxy-Connection: Keep-Alive

HTTP/1.1 504 Gateway Timeout
Date: Sun, 27 Mar 2022 10:17:59 GMT
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Connection: close`

but if I'll type capitalized ("Proxy-Authorization") as it wrote in RFC, then it will work without 504 gateway timeout error.
So question is - maybe you should rewrite name.rs file and replace all names with correct names from RFC?
I know that headers is case-insensitive, but it's normal practice to capitalize each word.

[seanmonstar]

This has been discussed several times before, see #228 (comment) for the current thinking.