In #32358 we added support to get InputStream through an HTTP Service interface. This involved detecting a return type of InputStream in RestClientAdapter, calling exchange with close=false, and returning (i.e. bypassing message converters).

We can push this further down into RestClient so it falls back on returning the InputStream of the response if no suitable message converter is found, and keeping the response open if the return value suggests it is yet to be consumed, e.g. InputStream or InputStreamResource.

The rational is the same as that of #32358, but making it built in RestClient, and requiring no special code in RestClientAdapter, also helping #36374. It will remove the surprise from using .retrieve(InputStreamResource.class) and having the response closed.

The alternative today is to call exchange and consume the response.