This commit introduces the following changes:
- Publisher -> Observable/Stream/etc. conversion is now managed
in a dedicated ConversionService instead of directly in
RequestBodyArgumentResolver and ResponseBodyResultHandler
- More isolated logic that decides if the stream should be
serialized as a JSON array or not
- Publisher<ByteBuffer> are now handled by regular
ByteBufferEncoder and ByteBufferDecoder
- Handle Publisher<Void> return value properly
- Ensure that the headers are properly written even for response
without body
- Improve JsonObjectEncoder to autodetect JSON arrays
adc50bbfb9