Allow one to specify server endpoint in config

[shouya]

I'm experimenting running aw-server-rust from my home k8s network, with a tls enabled ingress. However, when I trying point my local aw-client to the server I find no success - the config doesn't seem to allow me to specify an https endpoint address. Peeking into the code seems to indicate that the endpoint is hard-coded by stitching up a default protocol, and the host, port from config.

I guess there is no reason that it cannot support https, so I patched the source code like this. Now it worked perfectly for me. Would you like to accept it to the upstream?