Proxy selector

[technoweenie]

I started poking at the proxy code, and then decided trying to implement the net/http/httpproxy package in Go. Basically, I thought what it'd be like to replace 14 lines of code with my own version in 326 lines (plus docs):

faraday/lib/faraday/connection.rb

Lines 587 to 600 in e4b4b97

	if URI.parse('').respond_to?(:find_proxy)
	case url
	when String
	uri = Utils.URI(url)
	uri = URI.parse("#{uri.scheme}://#{uri.hostname}").find_proxy
	when URI
	uri = url.find_proxy
	when nil
	uri = find_default_proxy
	end
	else
	warn 'no_proxy is unsupported' if ENV['no_proxy'] || ENV['NO_PROXY']
	uri = find_default_proxy
	end

Three benefits:

1. no_proxy is correctly handled in cases where URI#find_proxy don't exist. I don't know what versions are affected, so this may be a moot point.
2. Potential speed improvements on repeat #proxy_for calls, especially with lots of no_proxy entries.
3. Actually support https_proxy

Is it worth it? I'm not really sure. But it was fun to write :)

[iMacTia]

Is it worth it? I'm not really sure. But it was fun to write :)

I just hope you don't expect me to maintain this 😂. Wouldn't know where to start from!

[iMacTia]

Ah for a moment I thought this was going to be Go code 🙄!
Looks good, but why not relying on the out-of-the-box method provided by Ruby? What are the main differences?

[technoweenie]

I listed the 3 benefits in the original PR message above. Basically, the code more correctly implements the environment vars, and it should be more efficient in long running scripts with the way it checks uri hosts against no_proxy.

I'm okay leaving this PR here until we're sure we want it. I extracted #1063 out of it too.

[iMacTia]

I have no doubts this can actually be better than the Ruby solution, I'm just a bit unconfident with reinventing the wheel (and then maintaining it). Is there any chance we can propose a fix on the Ruby implementation itself? Too audacious?