HTTP proxy support

The LucidLink client supports running behind an HTTP proxy that supports connect tunneling of TCP traffic. Basic authentication is supported. The proxy configuration is specified using a URL.

Note that only IP address is supported and not hostnames.

It can be passed either on the command line as a `--proxy` option on the `link`, `activate` and `update` commands, or in the LucidApp configuration file in ".lucid/app.json" with the "proxy" config parameter.

The current recommended way to connect via a proxy is to:

1) Make sure the Lucid client is stopped.

2) Find and edit the configuration file .lucid/app.json in your user's directory. Replace "127.0.0.1:8080" with the ip and port of the proxy server you wish to connect through:

3) To find your .lucid folder location open a Terminal Window or Windows Command Prompt and type lucid status and look for root directory.

{
  "restEndpoint": "127.0.0.1:7778",
  "stayConnected": false,
  "proxy": "127.0.0.1:8080"
}

3) Start the Lucid client. It should now try to connect via the proxy server specified in the configuration file.

Note that the proxy server needs to be an HTTP proxy server that supports HTTP tunneling (https://en.wikipedia.org/wiki/HTTP_tunnel#HTTP_CONNECT_method). The proxy server needs to allow tunneling of TCP traffic with destination port 443 (used for metadata synchronization) as well as HTTP(s) traffic to the object store.

SOCKS proxies are not supported.