[relay] Feature/relay integration (#2244)

This update adds new relay integration for NetBird clients. The new relay is based on web sockets and listens on a single port.

- Adds new relay implementation with websocket with single port relaying mechanism
- refactor peer connection logic, allowing upgrade and downgrade from/to P2P connection
- peer connections are faster since it connects first to relay and then upgrades to P2P
- maintains compatibility with old clients by not using the new relay
- updates infrastructure scripts with new relay service

encryption/letsencrypt.go

@@ -9,7 +9,7 @@ import (
 )
 
 // CreateCertManager wraps common logic of generating Let's encrypt certificate.
-func CreateCertManager(datadir string, letsencryptDomain string) (*autocert.Manager, error) {
+func CreateCertManager(datadir string, letsencryptDomain ...string) (*autocert.Manager, error) {
 	certDir := filepath.Join(datadir, "letsencrypt")
 
 	if _, err := os.Stat(certDir); os.IsNotExist(err) {
@@ -24,7 +24,7 @@ func CreateCertManager(datadir string, letsencryptDomain string) (*autocert.Mana
 	certManager := &autocert.Manager{
 		Prompt:     autocert.AcceptTOS,
 		Cache:      autocert.DirCache(certDir),
-		HostPolicy: autocert.HostWhitelist(letsencryptDomain),
+		HostPolicy: autocert.HostWhitelist(letsencryptDomain...),
 	}
 
 	return certManager, nil