Case insensitive headers

[cosmin-marginean]

I found an issue with cookie extraction on our test environment:

Upon further investigation, we realised the issue has to do with the set-cookie header (and potentially other headers?) not being treated in a case insensitive manner.

I presume the culprit is here https://github.com/jkcclemens/khttp/blob/master/src/main/kotlin/khttp/responses/GenericResponse.kt#L35 and it should be easy to patch (happy to provide a PR if that's acceptable).

[ArjixWasTaken]

Why is this still not fixed yet?