Feature/search domain for android (#1256)

Support search domain on Android

- pass list of search domains to Android SDK
- throw notification in case of search domain changes

client/internal/dns/notifier.go

@@ -0,0 +1,57 @@
+package dns
+
+import (
+	"reflect"
+	"sort"
+	"sync"
+
+	"github.com/netbirdio/netbird/client/internal/listener"
+)
+
+type notifier struct {
+	listener      listener.NetworkChangeListener
+	listenerMux   sync.Mutex
+	searchDomains []string
+}
+
+func newNotifier(initialSearchDomains []string) *notifier {
+	sort.Strings(initialSearchDomains)
+	return &notifier{
+		searchDomains: initialSearchDomains,
+	}
+}
+
+func (n *notifier) setListener(listener listener.NetworkChangeListener) {
+	n.listenerMux.Lock()
+	defer n.listenerMux.Unlock()
+	n.listener = listener
+}
+
+func (n *notifier) onNewSearchDomains(searchDomains []string) {
+	sort.Strings(searchDomains)
+
+	if len(n.searchDomains) != len(searchDomains) {
+		n.searchDomains = searchDomains
+		n.notify()
+		return
+	}
+
+	if reflect.DeepEqual(n.searchDomains, searchDomains) {
+		return
+	}
+
+	n.searchDomains = searchDomains
+	n.notify()
+}
+
+func (n *notifier) notify() {
+	n.listenerMux.Lock()
+	defer n.listenerMux.Unlock()
+	if n.listener == nil {
+		return
+	}
+
+	go func(l listener.NetworkChangeListener) {
+		l.OnNetworkChanged()
+	}(n.listener)
+}