MockServer: make MockResponse.body a Flow<ByteString>

[BoD]

In this PR, MockResponse.body becomes a Flow<ByteString> (previously was ByteString). This allows to not treat chunks as a special case.

The JS MockServer was also changed to use a net.Server (instead of http.Server), which allows sharing more common code (previously, MockServerCommon.writeResponse was used on JVM and Apple, but not JS).

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[martinbonnin]

Instead of adding a new parameter, could you do this instead?

  assertEquals(
      mockResponse.body.toList().fold(Buffer()) { buffer, byteString ->
        buffer.write(byteString)
      }.readByteString(),
      httpResponse.body!!.readByteString()
  )

This can suspend so you don't want to use it when delays are involved but I think so far it's only used in non-suspending code.

[BoD]

Arh it seemed like a good idea, but it's a bit tricky. When using chunked you pass something like c\r\nFirst chunk\n\r\nc\r\nSecond chunk\r\n0\r\n\r\n to the MockResponse but what you get in the HttpResponse is First chunk\nSecond chunk. So you can't really compare them as-is.

[martinbonnin]

Looks like we need a chunk decoder then ? Should be relatively easy to implement with all the okio/kotlin goodness?

[BoD]

Oh yeah that could work (in fact we already have chunk decoding code here 👍

[martinbonnin]

👍