Proxy for Async Http client.

[gkankanh]

Need some guidance on which async http client to use when behind a proxy for async S3 ops.
Netty client does not support proxy for async yet.

[debora-ito]

@gkankanh Providing proxy host and port is supported, you need to configure the Netty client on the S3 client's httpClientBuilder - see this comment for an example. Proxy authentication is not supported yet, we're tracking in #1432.

Let us know if this helps.