Support legacy HTTP servers that use only LF instead of CRLF

[clue]

As per https://tools.ietf.org/html/rfc7230#section-3.5 HTTP would require a CRLF, but apparently also accept a LF for robustness with legacy systems.

Resolves / closes #129

[kelunik]

@clue Could you share some insights which legacy servers use \n only? Nevermind, issue seems enough for me.

[clue]

@kelunik For the reference, I see you're already aware of #129. Other than that, I don't think that this is a particularly common problem, as this particular code didn't change over the last few years. That being said, I've linked to the relevant section of RFC 7230 above and don't see any reason why we wouldn't want to implement this for "robustness" with legacy servers.

[kelunik]

@clue The reason why you maybe don't want it is given in the RFC as well:

However, lenient parsing can result in security vulnerabilities if there are multiple recipients of the message and each has its own unique interpretation of robustness (see Section 9.5).

[clue]

@kelunik Thank you, I'm well aware and agree on the potential issues on lenient parsers. That being said, I don't see an actual issue here and the specs specifically suggest this behavior (please correct me if I'm wrong).

My vote would be to get this in as it fixes a relevant issue right now and of course we're happy to revisit this should this turn out to open new issues now or in the future 👍

[kelunik]

@clue I agree that it's probably fine in that case. 👍