[Feature request] Add mTLS (client certificate authentication) in nsclientV3

[nexero]

Client cert authentication (mTLS) is a method in TLS to additionally validate the client by using a client certificate (X.509).

I usually secure my exposed private services with mTLS in order to circumvent software vulnerabilities and resulting security flaws.

When requesting nsclientV3 to show the client cert from the Android Certificate Storage, BoringSSL in nsvlientV3 throws an exception OPENSSL_internal:TLSV1_ALERT_CERTIFICATE_REQUIRED.

What I'd expect is a popup selector for selecting the desired client cert instead of just an error message in the log.

I don't know if nsclientV3 plugin is the right place to begin with an implementation or if it should be part of nssdk instead...