Replace webrick with a small/simple custom rack-compatible http server

[bensheldon]

I would like to drop the runtime dependency on webrick. Webrick is only used for the probe server functionality which is intended to be a private interface.

I think webrick could be replaced with <100 lines of Ruby to implement a bare minimum http server to be used for the probe server, thus it would only need to implement simple GET and string paths, and not do other query-parsing/etc.

[dixpac]

Can I take this?

[bensheldon]

@dixpac yes please 🙏

[bensheldon]

And to calibrate the level of polish I'm expecting (low): I have previously fed this into GitHub Copilot and ChatGPT and the result seemed fine. There already is some integration testing, so maybe 1 or 2 more test cases in this pattern should be sufficient:

good_job/spec/lib/good_job/probe_server_spec.rb

Lines 14 to 30 in 3bc2f85

	describe '#start' do
	it 'starts a webrick server that binds to all interfaces' do
	probe_server.start
	wait_until(max: 1) { expect(probe_server).to be_running }
	ip_addresses = Socket.ip_address_list.select(&:ipv4?).map(&:ip_address)
	expect(ip_addresses.size).to be >= 2
	expect(ip_addresses).to include("127.0.0.1")
	aggregate_failures do
	ip_addresses.each do |ip_address|
	response = Net::HTTP.get(ip_address, "/", port)
	expect(response).to eq("OK")
	end
	end
	end
	end