[management] Add API of new network concept (#3012)

management/server/util/util.go

@@ -0,0 +1,16 @@
+package util
+
+// Difference returns the elements in `a` that aren't in `b`.
+func Difference(a, b []string) []string {
+	mb := make(map[string]struct{}, len(b))
+	for _, x := range b {
+		mb[x] = struct{}{}
+	}
+	var diff []string
+	for _, x := range a {
+		if _, found := mb[x]; !found {
+			diff = append(diff, x)
+		}
+	}
+	return diff
+}