[#1183] node/notificator: Implement notificator

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/services/notificator/deps.go

@@ -0,0 +1,18 @@
+package notificator
+
+import objectSDKAddress "github.com/nspcc-dev/neofs-sdk-go/object/address"
+
+// NotificationSource is a source of object notifications.
+type NotificationSource interface {
+	// Iterate must iterate over all notifications for the
+	// provided epoch and call handler for all of them.
+	Iterate(epoch uint64, handler func(topic string, addr *objectSDKAddress.Address))
+}
+
+// NotificationWriter notifies all the subscribers
+// about new object notifications.
+type NotificationWriter interface {
+	// Notify must send string representation of the object
+	// address into the specified topic.
+	Notify(topic string, address *objectSDKAddress.Address)
+}