Add support for HTTP_PROXY and SOCKS_PROXY

[unclearParadigm]

Hi @sigaloid,

It has been a while since I initially proposed to add Support for Proxies. The project was still called LibReddit at that time - see original request: libreddit/libreddit#841 .

Further Issues that relate to that

• 💡 Feature request: HTTP / SOCKS proxy support #339
• 🐛 Bug Report: System http(s)_proxy variable ignored #184
• 💡 Feature request: Add Tor tunneling option #1

Since my instance is getting rate-limited frequently, people are already complaining about it, and I don't want to add further VPS (with new public IPs) just to circumvent the rate-limiting. So I finally decided to patch redlib to support HTTP_PROXY and SOCKS proxies.

Changes in this MR

Redlib honors the following Environment-Variables:

• HTTP_PROXY
• HTTPS_PROXY
• SOCKS_PROXY

if SOCKS_PROXY is set, it'll take precedence over HTTPS_PROXY and HTTP_PROXY. Additionally the Environment Variables support authentication using the following format scheme://username:password@host:port (e.g. http://proxyUsername:mySuperSecureProxyPassword@localhost:8090).

For SOCKS support I introduced tokio-socks as dependency. For HTTP Proxy support, I just wrote a simple HTTP CONNECT wrapper. In all cases, consumers of the CLIENT won't notice a difference.

Tests

I have tested HTTP Proxying with TinyProxy locally. And I have tested SOCKS Proxying with my VPN Providers SOCKS Proxy, and TOR proxying through a local tor-socks-proxy container.

Would appreciate if you could review this MR - and maybe merge back. That'd make the world a better place - at least get rid of some rate-limits ^^

Cheers,
ruffy