Add :downcase_request_headers option to HTTP1.connect

[DunyaKokoschka]

i hear you want not lower header. i give you not lower header. but also i make default headers not lower if you pass
in not lower option. alexi say this change is slow. i tell alexi if you care about slow why using elixir.

#256

[whatyouhide]

Do you know if this is a behavior that we should have for HTTP/2 as well?

[ericmj]

Do you know if this is a behavior that we should have for HTTP/2 as well?

I would say no until proven otherwise. AFAIK all HTTP/2 implementers properly handle header casing.

[DunyaKokoschka]

I've added some commits which address the comments. The name of the option is currently case_sensitive_headers. And I added the docs for the option to the Mint.HTTP1.connect method. I'm not sure if this is the correct place. I wasn't so sure about this comment: case_sensitive_headers

Also, locally the twitter integration test is failing for me with a 302 instead of a 200.

[coveralls]

Pull Request Test Coverage Report for Build af90beafc56cae431db21473789a981195337f07-PR-399

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 20 of 20 (100.0%) changed or added relevant lines in 5 files are covered.
• 62 unchanged lines in 5 files lost coverage.
• Overall coverage increased (+0.05%) to 87.674%

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Files with Coverage Reduction	New Missed Lines	%
lib/mint/core/util.ex	2	91.3%
lib/mint/http2.ex	3	94.35%
lib/mint/http1/response.ex	4	69.23%
lib/mint/http.ex	13	62.86%
lib/mint/http1.ex	40	83.86%

Totals
Change from base Build 301b77910b131541c11ef8b34d8d6f6b7c0583d1:	0.05%
Covered Lines:	1259
Relevant Lines:	1436

---

💛 - Coveralls

[ericmj]

@whatyouhide I rebased and did some clean up. Do you think we are good to merge this?

[wojtekmach]

Suggested change

	because http/1.1 header names are not case-insensitive.
	because HTTP/1.1 header names are case-sensitive.

[ericmj]

Oh wait. This text is even wrong, we can lower because they are in fact case-insensitive.

[wojtekmach]

I believe I mentioned it on some other occasion: "trailer headers" feels like a misnomer. Quickly looking at RFC 7231 the naming didn't seem to be super explicit, but in the newer one that surpasses it, RFC 9110, it is: http has fields: header fields (colloquially "headers") and trailer fields (colloquially "trailers")

I only mention this as an offer to send a patch to use "trailers" or "trailer fields" naming internally. It's probably not worth it to go through deprecations if the trailer_headers name was used in public APIs so I wouldn't touch these.

Feel free to ignore, it's not a big deal in the grand scheme of things. :)

[whatyouhide]

Beautiful Eric, couple of comments but we can finally ship this, exciting!!