[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/server/server.go

@@ -0,0 +1,76 @@
+package server
+
+import (
+	"context"
+	"crypto/tls"
+
+	log "github.com/sirupsen/logrus"
+	"go.opentelemetry.io/otel/metric"
+
+	"github.com/netbirdio/netbird/relay/auth"
+	"github.com/netbirdio/netbird/relay/server/listener"
+	"github.com/netbirdio/netbird/relay/server/listener/ws"
+)
+
+// ListenerConfig is the configuration for the listener.
+// Address: the address to bind the listener to. It could be an address behind a reverse proxy.
+// TLSConfig: the TLS configuration for the listener.
+type ListenerConfig struct {
+	Address   string
+	TLSConfig *tls.Config
+}
+
+// Server is the main entry point for the relay server.
+// It is the gate between the WebSocket listener and the Relay server logic.
+// In a new HTTP connection, the server will accept the connection and pass it to the Relay server via the Accept method.
+type Server struct {
+	relay      *Relay
+	wSListener listener.Listener
+}
+
+// NewServer creates a new relay server instance.
+// meter: the OpenTelemetry meter
+// exposedAddress: this address will be used as the instance URL. It should be a domain:port format.
+// tlsSupport: if true, the server will support TLS
+// authValidator: the auth validator to use for the server
+func NewServer(meter metric.Meter, exposedAddress string, tlsSupport bool, authValidator auth.Validator) (*Server, error) {
+	relay, err := NewRelay(meter, exposedAddress, tlsSupport, authValidator)
+	if err != nil {
+		return nil, err
+	}
+	return &Server{
+		relay: relay,
+	}, nil
+}
+
+// Listen starts the relay server.
+func (r *Server) Listen(cfg ListenerConfig) error {
+	r.wSListener = &ws.Listener{
+		Address:   cfg.Address,
+		TLSConfig: cfg.TLSConfig,
+	}
+
+	wslErr := r.wSListener.Listen(r.relay.Accept)
+	if wslErr != nil {
+		log.Errorf("failed to bind ws server: %s", wslErr)
+	}
+
+	return wslErr
+}
+
+// Shutdown stops the relay server. If there are active connections, they will be closed gracefully. In case of a context,
+// the connections will be forcefully closed.
+func (r *Server) Shutdown(ctx context.Context) (err error) {
+	// stop service new connections
+	if r.wSListener != nil {
+		err = r.wSListener.Shutdown(ctx)
+	}
+
+	r.relay.Shutdown(ctx)
+	return
+}
+
+// InstanceURL returns the instance URL of the relay server.
+func (r *Server) InstanceURL() string {
+	return r.relay.instanceURL
+}