Add support for mTLS

[mg-dd]

This PR fixes two issues:

#194
#234

The background is that the TLS connection established by the proxy agents do not add the required parameters for mTLS / self-signed CAs. This PR adds a way to provide these parameters. The general approach was taken from the feedback from this PR: https://github.com/TooTallNate/proxy-agents/pull/195/files

ptal @TooTallNate

[changeset-bot]

🦋 Changeset detected

Latest commit: 041a7c5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
https-proxy-agent	Minor
socks-proxy-agent	Minor
agent-base	Minor

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[TooTallNate]

Great looking PR! Thank you so much. I have some feedback, but once that's addressed I'll be happy to merge this.

[TooTallNate]

Seems weird to me that socket is optional. Also, let's make it the first parameter:

Suggested change

	servername: string | undefined,
	opts: tls.ConnectionOptions,
	socket?: net.Socket,
	socket: net.Socket,
	servername: string | undefined,
	opts: tls.ConnectionOptions,

[mg-dd]

The reason it was optional was that pac-proxy-agent calls tls.connect without providing a socket. I've made your suggested changes and reverted the changes to pac-proxy-agent for now. Let me know how you would like to proceed in that regard.

[TooTallNate]

I see. How about if we do something like this in pac-proxy-agent?

	socket = net.connect(opts);
	
	if (secureEndpoint) {
		const servername = opts.servername || opts.host;
		socket = this.upgradeSocketToTls(
			socket,
			servername,
			opts
		);
	}

[patrickheeney]

@mg-dd Great PR! I need something similar, do you need any help pushing this over the finish line?

[mg-dd]

@TooTallNate this is ready for another look. The only open question is how you would like to handle the TLS connection in pac-proxy-agent.

[brunobastosg]

Hi, any news on this? I also need this feature.

[amirbilu]

Any news on this?

[cptRaclette]

@TooTallNate: Would love to see this feature in the proxy agents. Is there anything left to do?

[orlando1108]

HI, any update about this PR ? 💯

[marcchambon]

Thank you soo much for maintaining this awesome project !
Any news ?

[sibelius]

can we move forward on this?

what is missing?

[pebie]

Thank you for this PR !
@TooTallNate Any news about moving forward ?

🙏 🙏

[sibelius]

we are using a patch of this pull request in production and it is working well