This commit changes the write methods to return `Flux<DataBuffer>` instead of `Mono<Void>`, giving access to the original buffers, so that they can decided whether the buffers need to be closed or not. Issue: SPR-15726
This commit changes the write methods to return `Flux<DataBuffer>` instead of `Mono<Void>`, giving access to the original buffers, so that they can decided whether the buffers need to be closed or not. Issue: SPR-15726