[Feature] Support 'allowPartialChunks' in the HttpDecoderSpec

[reta]

Motivation

The Netty's HttpDecoderConfig exposes allowPartialChunks property which hints the HttpObjectDecoded if the chunk could be split into multiple when chunk exceeds the readable bytes. The HttpDecoderSpec sadly does not provide the way to configure it.

Desired solution

Support 'allowPartialChunks' in the HttpDecoderSpec so it could be used to create HttpDecoderConfig instances with respective property set.

Considered alternatives

N/A

Additional context

We right now are running into an issue when the complete chunk should be consumed but the partial ones are being produced instead.

@violetagg I am happy to submit the pull request if the feature makes sense to you, thank you

[violetagg]

@reta We love PRs :)
Please base it on 1.1.x branch.