Support http config

[roidelapluie]

• Pass basic auth parameters
• Pass TLS client parameters

[rustycl0ck]

Any suggestions on how to achieve this? From here:

we should probably use Prometheus client tls config

Does this mean that for TLS config and for auth, we should use the same configuration file syntax used by prometheus? or does this mean that we should something from the github.com/prometheus/client_golang/prometheus package or github.com/prometheus/client_golang/prometheus/promhttp somehow? or maybe both?

Otherwise I can directly use regular crypto/tls and net/http to achieve this easily by replacing

        client := &http.Client{}

with:

        tlsConfig := &tls.Config{}
        transport := &http.Transport{TLSClientConfig: tlsConfig}
        client := &http.Client{Transport: transport}

Just trying to understand what is the recommended approach for prometheus exporters.

[roidelapluie]

HTTPClientConfig from github.com/prometheus/common/config

and then NewRoundTripperFromConfig

[rustycl0ck]

This has been fixed in #49