[roq-server] Support connectivity thorugh HTTP proxy

[thraneh]

No description provided.

[thraneh]

This has been implemented and the REST URI flags have typically been complimented with a proxy such that if --rest_uri is the final end-point then --rest_proxy is the (optional) proxy end-point.

HTTP requests will only include the host in the request path if a proxy has been specified.

The scheme must be specified when connecting to the proxy, e.g. --rest_proxy https://localhost:1234.

This has not yet been tested with any specific client proxy.
There may therefore be specific requirements that are not yet dealt with.

[thraneh]

This was tested and found not to be working. It appears that the TLS connection couldn't be established. Re-opening this issue to investigate.