TCP client command (#1696)

* add cli commands

* add jwt cache test

* add tcptunnel test

* add stdin/stdout support

* use cryptutil hash function

* doc updates

* fix log timestamp

internal/authclient/config.go

@@ -0,0 +1,27 @@
+package authclient
+
+import (
+	"crypto/tls"
+)
+
+type config struct {
+	tlsConfig *tls.Config
+}
+
+func getConfig(options ...Option) *config {
+	cfg := new(config)
+	for _, o := range options {
+		o(cfg)
+	}
+	return cfg
+}
+
+// An Option modifies the config.
+type Option func(*config)
+
+// WithTLSConfig returns an option to configure the tls config.
+func WithTLSConfig(tlsConfig *tls.Config) Option {
+	return func(cfg *config) {
+		cfg.tlsConfig = tlsConfig
+	}
+}