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/tcptunnel/config.go

@@ -0,0 +1,60 @@
+package tcptunnel
+
+import (
+	"crypto/tls"
+
+	"github.com/pomerium/pomerium/internal/cliutil"
+	"github.com/pomerium/pomerium/internal/log"
+)
+
+type config struct {
+	jwtCache  cliutil.JWTCache
+	dstHost   string
+	proxyHost string
+	tlsConfig *tls.Config
+}
+
+func getConfig(options ...Option) *config {
+	cfg := new(config)
+	if jwtCache, err := cliutil.NewLocalJWTCache(); err == nil {
+		WithJWTCache(jwtCache)(cfg)
+	} else {
+		log.Error().Err(err).Msg("tcptunnel: error creating local JWT cache, using in-memory JWT cache")
+		WithJWTCache(cliutil.NewMemoryJWTCache())(cfg)
+	}
+	for _, o := range options {
+		o(cfg)
+	}
+	return cfg
+}
+
+// An Option modifies the config.
+type Option func(*config)
+
+// WithDestinationHost returns an option to configure the destination host.
+func WithDestinationHost(dstHost string) Option {
+	return func(cfg *config) {
+		cfg.dstHost = dstHost
+	}
+}
+
+// WithJWTCache returns an option to configure the jwt cache.
+func WithJWTCache(jwtCache cliutil.JWTCache) Option {
+	return func(cfg *config) {
+		cfg.jwtCache = jwtCache
+	}
+}
+
+// WithProxyHost returns an option to configure the proxy host.
+func WithProxyHost(proxyHost string) Option {
+	return func(cfg *config) {
+		cfg.proxyHost = proxyHost
+	}
+}
+
+// WithTLSConfig returns an option to configure the tls config.
+func WithTLSConfig(tlsConfig *tls.Config) Option {
+	return func(cfg *config) {
+		cfg.tlsConfig = tlsConfig
+	}
+}