[client] refactor lazy detection (#4050)

This PR introduces a new inactivity package responsible for monitoring peer activity and notifying when peers become inactive.
Introduces a new Signal message type to close the peer connection after the idle timeout is reached.
Periodically checks the last activity of registered peers via a Bind interface.
Notifies via a channel when peers exceed a configurable inactivity threshold.
Default settings
DefaultInactivityThreshold is set to 15 minutes, with a minimum allowed threshold of 1 minute.

Limitations
This inactivity check does not support kernel WireGuard integration. In kernel–user space communication, the user space side will always be responsible for closing the connection.

client/internal/lazyconn/inactivity/manager_test.go

@@ -0,0 +1,113 @@
+package inactivity
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/netbirdio/netbird/client/internal/lazyconn"
+)
+
+type mockWgInterface struct {
+	lastActivities map[string]time.Time
+}
+
+func (m *mockWgInterface) LastActivities() map[string]time.Time {
+	return m.lastActivities
+}
+
+func TestPeerTriggersInactivity(t *testing.T) {
+	peerID := "peer1"
+
+	wgMock := &mockWgInterface{
+		lastActivities: map[string]time.Time{
+			peerID: time.Now().Add(-20 * time.Minute),
+		},
+	}
+
+	fakeTick := make(chan time.Time, 1)
+	newTicker = func(d time.Duration) Ticker {
+		return &fakeTickerMock{CChan: fakeTick}
+	}
+
+	peerLog := log.WithField("peer", peerID)
+	peerCfg := &lazyconn.PeerConfig{
+		PublicKey: peerID,
+		Log:       peerLog,
+	}
+
+	manager := NewManager(wgMock, nil)
+	manager.AddPeer(peerCfg)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// Start the manager in a goroutine
+	go manager.Start(ctx)
+
+	// Send a tick to simulate time passage
+	fakeTick <- time.Now()
+
+	// Check if peer appears on inactivePeersChan
+	select {
+	case inactivePeers := <-manager.inactivePeersChan:
+		assert.Contains(t, inactivePeers, peerID, "expected peer to be marked inactive")
+	case <-time.After(1 * time.Second):
+		t.Fatal("expected inactivity event, but none received")
+	}
+}
+
+func TestPeerTriggersActivity(t *testing.T) {
+	peerID := "peer1"
+
+	wgMock := &mockWgInterface{
+		lastActivities: map[string]time.Time{
+			peerID: time.Now().Add(-5 * time.Minute),
+		},
+	}
+
+	fakeTick := make(chan time.Time, 1)
+	newTicker = func(d time.Duration) Ticker {
+		return &fakeTickerMock{CChan: fakeTick}
+	}
+
+	peerLog := log.WithField("peer", peerID)
+	peerCfg := &lazyconn.PeerConfig{
+		PublicKey: peerID,
+		Log:       peerLog,
+	}
+
+	manager := NewManager(wgMock, nil)
+	manager.AddPeer(peerCfg)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// Start the manager in a goroutine
+	go manager.Start(ctx)
+
+	// Send a tick to simulate time passage
+	fakeTick <- time.Now()
+
+	// Check if peer appears on inactivePeersChan
+	select {
+	case <-manager.inactivePeersChan:
+		t.Fatal("expected inactive peer to be marked inactive")
+	case <-time.After(1 * time.Second):
+		// No inactivity event should be received
+	}
+}
+
+// fakeTickerMock implements Ticker interface for testing
+type fakeTickerMock struct {
+	CChan chan time.Time
+}
+
+func (f *fakeTickerMock) C() <-chan time.Time {
+	return f.CChan
+}
+
+func (f *fakeTickerMock) Stop() {}