[ADD] Support for https redirect URIs (TLS)

[trembel]

This commit adds support for TLS-encrypted redirect URIs. The commit adds a second server for https:

1. Binding a new TCP socket
2. Uses rcgen to generate a new TLS certificate (only in memory)
3. Uses rustls to do the TLS handshake and convert the TCPStream into a TLS stream
4. Generalizes the request function (and its dependent) to accept an object implementing Read + Write instead of just TCPStream
5. Redirects all redirect_uri that contain https to the https server

This last point I think can be discussed: Should all redirect uri's containing https be redirected to the https server or only the redirect uri's containing localhost? IMO it should not make a difference, as all https URIs will support TLS.

Also: the self-signed certificate is not trusted per default (at least on Firefox), so one has to go "Advanced" -> "Accept Risk ..." in Firefox when being redirected. For me this is no issue, if it is one, we could save the TLS certificate to the apropriate location(s) (requiring sudo).

I have not tested this commit across a http URI, just because I have no OAuth provider except of Microsoft (for hotmail). This commit solves #40.

[ltratt]

Thanks for this -- this looks really good!

[trembel]

Thanks for review, I will take care later today.

[ltratt]

This is excellent, thanks! I need to think a bit about if/where we store certificates, and so on, but that's a luxury add on: this PR does the hard bit.

[ltratt]

If you force push a rustfmt, I'll merge this.

[trembel]

Sure, thanks a lot for the quick process! rustfmt is pushed.

[ltratt]

Thanks!