Support ECDSA certificates

[valpackett]

Is your feature request related to a problem? Please describe.

See LizardByte/Sunshine#1353

Sunshine currently uses the same TLS certificate for both the web UI and communication with Moonlight. It is desirable to not have self-signed certs on the web UI, and @tailscale users are always tempted to run any local service with legit certs because it's really easy to get a Let's Encrypt one with tailscale cert. Since LE switched to Elliptic Curve by default, those are the type you get with that command, and currently there's no option to request a particular type (tailscale/tailscale#9768).

When moonlight-qt connects to a server with such a certificate, pairing fails with a rather nondescript error in the UI, with "MITM detected" logged on the console.

Describe the solution you'd like

Implement support for ECDSA certificates.

Probably at first also show a warning when one is used, to inform the user that other clients may not support these.

Describe alternatives you've considered

🤷‍♀️

[cgutman]

ECDSA should be supported as of c63b918 (not yet released). Please try a nightly build and see if that works for you.

I'm not sure which platform you are using, but you can find Windows, Mac, Steam Link, and AppImage builds here: https://ci.appveyor.com/project/cgutman/moonlight-qt/branch/master