Support TLS configuration for upstream

[sumeet-zuora]

when using https endpoint, I am getting http: proxy error: x509: certificate signed by unknown authority is there a way to allow insecure upstream

[simonpasquier]

👋 this isn't currently possible. I'd say that users should be able to configure the usual TLS settings for the upstream server: CA file, client cert/key file, server name and skip verification.