Feature/android route notification (#868)

Add new feature to notify the user when new client route has arrived.
Refactor the initial route handling. I move every route logic into the route
manager package.

* Add notification management for client rules
* Export the route notification for Android
* Compare the notification based on network range instead of id.

client/internal/routemanager/notifier.go

@@ -0,0 +1,86 @@
+package routemanager
+
+import (
+	"sort"
+	"sync"
+
+	"github.com/netbirdio/netbird/route"
+)
+
+// RouteListener is a callback interface for mobile system
+type RouteListener interface {
+	// OnNewRouteSetting invoke when new route setting has been arrived
+	OnNewRouteSetting()
+}
+
+type notifier struct {
+	initialRouteRangers []string
+	routeRangers        []string
+
+	routeListener    RouteListener
+	routeListenerMux sync.Mutex
+}
+
+func newNotifier() *notifier {
+	return &notifier{}
+}
+
+func (n *notifier) setListener(listener RouteListener) {
+	n.routeListenerMux.Lock()
+	defer n.routeListenerMux.Unlock()
+	n.routeListener = listener
+}
+
+func (n *notifier) setInitialClientRoutes(clientRoutes []*route.Route) {
+	nets := make([]string, 0)
+	for _, r := range clientRoutes {
+		nets = append(nets, r.Network.String())
+	}
+	sort.Strings(nets)
+	n.initialRouteRangers = nets
+}
+
+func (n *notifier) onNewRoutes(idMap map[string][]*route.Route) {
+	newNets := make([]string, 0)
+	for _, routes := range idMap {
+		for _, r := range routes {
+			newNets = append(newNets, r.Network.String())
+		}
+	}
+
+	sort.Strings(newNets)
+	if !n.hasDiff(n.routeRangers, newNets) {
+		return
+	}
+
+	n.routeRangers = newNets
+
+	if !n.hasDiff(n.initialRouteRangers, newNets) {
+		return
+	}
+	n.notify()
+}
+
+func (n *notifier) notify() {
+	n.routeListenerMux.Lock()
+	defer n.routeListenerMux.Unlock()
+	if n.routeListener == nil {
+		return
+	}
+
+	go func(l RouteListener) {
+		l.OnNewRouteSetting()
+	}(n.routeListener)
+}
+
+func (n *notifier) hasDiff(a []string, b []string) bool {
+	if len(a) != len(b) {
+		return true
+	}
+	for i, v := range a {
+		if v != b[i] {
+			return true
+		}
+	}
+	return false
+}