[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

relay/messages/auth/auth.go

@@ -0,0 +1,51 @@
+package auth
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+)
+
+type Algorithm int
+
+const (
+	AlgoUnknown Algorithm = iota
+	AlgoHMACSHA256
+	AlgoHMACSHA512
+)
+
+func (a Algorithm) String() string {
+	switch a {
+	case AlgoHMACSHA256:
+		return "HMAC-SHA256"
+	case AlgoHMACSHA512:
+		return "HMAC-SHA512"
+	default:
+		return "Unknown"
+	}
+}
+
+type Msg struct {
+	AuthAlgorithm  Algorithm
+	AdditionalData []byte
+}
+
+func (msg *Msg) Marshal() ([]byte, error) {
+	var buf bytes.Buffer
+	enc := gob.NewEncoder(&buf)
+	if err := enc.Encode(msg); err != nil {
+		return nil, fmt.Errorf("encode Msg: %w", err)
+	}
+	return buf.Bytes(), nil
+}
+
+func UnmarshalMsg(data []byte) (*Msg, error) {
+	var msg *Msg
+
+	buf := bytes.NewBuffer(data)
+	dec := gob.NewDecoder(buf)
+	if err := dec.Decode(&msg); err != nil {
+		return nil, fmt.Errorf("decode Msg: %w", err)
+	}
+	return msg, nil
+}