All backends write headers as UTF-8

[ghik]

Requires softwaremill/sttp-model#336 and closes softwaremill/sttp-model#317

[ghik]

I decided to extract this class because it makes it clear that it's the AsyncHttpClient that does not support non-ascii header fields, which would not be apparent if this method was overridden in every AsyncHttpClient*HttpTest.

[adamw]

That's a good idea, but probably there are more such common flags that are set in each test class individually which could be de-duplicated here

[ghik]

I'll go through them and see what else I can extract.

[ghik]

@adamw seems like sttp-model dropped support for Scala 2.11 while sttp still retains it. What should we do?

[adamw]

Ah it's the v3 branch ... let's drop 2.11 here as well, since we got so far ;)

[ghik]

Or maybe a more sensible thing to do would be to backport the sttp-model changes to the version used in sttp3, i.e. 1.5.x, while using 1.7.9 in master of sttp?

[adamw]

I think we'll be maintaining the v3 branch for a while, and maintaining too many forks across projects is just too much work. So if we need to drop 2.11, let's do it :)

[ghik]

There would be no forks involved, only a bugfix targeting a slightly earlier version (1.5.x instead of 1.7.x, which is probably what I should have done from the beginning). But if you think it's fine to drop 2.11 for v3 and use newest sttp-model then sure, I won't hesitate :)

[adamw]

My worry is that this won't be the last fix in sttp-model that we'll want to use in sttp3, so we'll have to maintain two sttp branches (v3 & main), plus two sttp-model branches. I don't want to go that route ;)

[adamw]

Looks good :)