Support for use of webproxy

[andloh]

Describe the bug

This is more of a feature request. Add support to reach the internet (github) through a webproxy.
This is probably already works with the use of HTTP/S_PROXY envvars, but only if you are using PAT for authentication, not for deployment keys.

If your gonna use deployment keys behind a proxy, ssh needs to know how to tunnel the connection. With the use of socat and proxycommand for your ~/.ssh/config, this can be achieved with the following:

host github.com
    hostname ssh.github.com
    port 443
    proxycommand socat - PROXY:your.proxy.ip:%h:%p,proxyport=3128,proxyauth=user:pwd

To do this today with flux2, we have to create our own custom image with socat installed and this config as a configmap + config in the targeted deployment to map the config. This makes it hard to manage and upgrade flux2

Expected behavior

A flag in the installation process to specify your proxy-needs and socat or another similar tool to handle SOCKS in the targeted containers

Below please provide the output of the following commands:

flux --version flux version 0.8.1

[stefanprodan]

Duplicate of: fluxcd/source-controller#131