Add .resourceUsingClient to HttpClient backends.

[kamilkloch]

Rationale:
I am trying to migrate away from the deprecated AsyncHttpClientFs2Backend and am struggling to reproduce the functionality with

sttp/effects/fs2/src/main/scalajvm/sttp/client3/httpclient/fs2/HttpClientFs2Backend.scala

Line 96 in b387e2f

object HttpClientFs2Backend {

.
HttpClientFs2Backend.resource has a default http client baked in, HttpClientFs2Backend.usingClient has hard-coded flag closeClient = false. I am missing something akin to HttpClientFs2Backend.resourceUsingClient, which would allow me to customize the client and at the same time get back the resource.

[adamw]

Sure, sounds good :) Maybe we could add similar methods to other HttpClient backend variants (where it makes sense)

[kamilkloch]

I added methods to 2 other client variants. Surprisingly, ZIO backend already contains HttpClientZioBackend.layerUsingClient, but its implementation calls usingClient, which sets closeClient flag to false. Is that the desired behavior? (HttpClientZioBackend.layer sets the flag to true).

[adamw]

@kamilkloch Yes, in ZIO the equivalent would be scopedUsingClient. A layer is just a description of how to create an object, lifted into ZIO-land. Scope is ZIO's Resource, where closing happens.

[kamilkloch]

@adamw I understand. However, the flag closeClient is flipped (Scope vs Resource). Why is that?
My bad, now I see (scope vs layer)

[adamw]

Thank you :)

[kamilkloch]

Do we want to update the documentstion as well, or leave out this flavor?

[adamw]

Ah the docs - yes of course :)