When elasticsearch is behind a Proxy and this Proxy does not support GET with body (which might be seen as a bug of the Proxy), people can't use our Java Rest Client as explained in https://discuss.elastic.co/t/es-cluster-via-proxy-ip-but-listener-timeout-after-waiting-for-30000-ms/116192/6

For example, the search Request here uses a GET method:

I think we should may be switch to POST instead anytime we might have a body.

Thoughts?