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

client/internal/peer/conn.go

@@ -419,3 +419,7 @@ func (conn *Conn) OnRemoteCandidate(candidate ice.Candidate) {
 		}
 	}()
 }
+
+func (conn *Conn) GetKey() string {
+	return conn.config.Key
+}