[v3] Enable RestResponse<headers, Mono<TBody>>

[anuchandy]

The DecodedResponse has the capability to emit lazy decoded body, bubble up this to RestResponseBase level so that we can support RestResponseBase<..., Mono<TBody>>

[anuchandy]

@JonathanGiles as you pointed this is supported by .net (via T Task.Result)

[anuchandy]

RestResponse of this type should be Closable. When user subscribe outer mono:

Mono<RestResponseBase<..., Mono<TBody>>>

the request will be initiated then RestResponse will be created and emitted from the returned response.
The content will be drained only if user subscribe to Mono<TBody>, if user don't read the body then we need the ability to release the content hence closable.

[anuchandy]

The proxy interface looks like:

    @Host("http://httpbin.org")
    private interface HttpBinService {
        @PUT("put")
        Mono<RestResponseBase<HttpBinHeaders,Mono<HttpBinJSON>>> putBodyAndHeadersAsyncContentAsync(@BodyParam(ContentType.APPLICATION_OCTET_STREAM) String body);

        @PUT("put")
        RestResponseBase<HttpBinHeaders,Mono<HttpBinJSON>> putBodyAndHeadersContentAsync(@BodyParam(ContentType.APPLICATION_OCTET_STREAM) String body);
    }

The usage looks like:

Both response and body is async

final Mono<RestResponseBase<HttpBinHeaders, Mono<HttpBinJSON>>> asyncResponse = createService(HttpBinService.class)
        .putBodyAndHeadersAsyncContentAsync("body string");
//
asyncResponse.flatMap(response -> {
    //
    final Mono<HttpBinJSON> asyncBody = response.body();
    return asyncBody.flatMap(body -> {
        // "body string"
        System.out.println(body.data);
        return Mono.just(response.headers());
    });
})
.doOnNext(hdrs -> {
    final HttpBinHeaders headers = hdrs;
    System.out.println(headers.connection.toLowerCase());
})
.block();

response is sync and body is async

final RestResponseBase<HttpBinHeaders, Mono<HttpBinJSON>> response = createService(HttpBinService.class)
        .putBodyAndHeadersContentAsync("body string");
//
final Mono<HttpBinJSON> asyncBody = response.body();
asyncBody.doOnNext(body -> {
            // "body string"
        System.out.println(body.data);
})
.block();

final HttpBinHeaders headers = response.headers();
System.out.println(headers.connection.toLowerCase());