Support new Management service protocol (NetworkMap) (#193)

* feature: support new management service protocol

* chore: add more logging to track networkmap serial

* refactor: organize peer update code in engine

* chore: fix lint issues

* refactor: extract Signal client interface

* test: add signal client mock

* refactor: introduce Management Service client interface

* chore: place management and signal clients mocks to respective packages

* test: add Serial test to the engine

* fix: lint issues

* test: unit tests for a networkMapUpdate

* test: unit tests Sync update

util/common.go

@@ -0,0 +1,16 @@
+package util
+
+// SliceDiff returns the elements in slice `x` that are not in slice `y`
+func SliceDiff(x, y []string) []string {
+	mapY := make(map[string]struct{}, len(y))
+	for _, val := range y {
+		mapY[val] = struct{}{}
+	}
+	var diff []string
+	for _, val := range x {
+		if _, found := mapY[val]; !found {
+			diff = append(diff, val)
+		}
+	}
+	return diff
+}