refactor: user client and proxy handling; remove unused auth code

common/utils/netutil/proxy.go

@@ -0,0 +1,15 @@
+package netutil
+
+import (
+	"net/url"
+
+	"golang.org/x/net/proxy"
+)
+
+func NewProxyDialer(proxyUrl string) (proxy.Dialer, error) {
+	url, err := url.Parse(proxyUrl)
+	if err != nil {
+		return nil, err
+	}
+	return proxy.FromURL(url, proxy.Direct)
+}