Support http proxy authentication in Netty gRPC usage

[ray-roestenburg-da]

We support setting http forward proxy using https.proxyHost and https.proxyPort, which is automatically picked up by JwkProvider, gRPC (netty) and we've added support for this where we use pekko-http (this does already support https.proxyUser and httpsProxyPassword).

https.proxyUser and httpsProxyPassword is not supported yet in gRPC since that needs some extra work for instance with below example:

  class ProxyAuthenticator extends Authenticator{
    override def getPasswordAuthentication: PasswordAuthentication = new PasswordAuthentication("testuser", "testpassword".toCharArray)
  }

  Authenticator.setDefault(new ProxyAuthenticator)