feat(microservices) make packets more lightweight

packages/microservices/test/client/client-nats.spec.ts

@@ -105,7 +105,6 @@ describe('ClientNats', () => {
     const msg = { pattern, data: 'data', id: '1' };
     let callback: sinon.SinonSpy, subscription;
     const responseMessage = {
-      err: null,
       response: 'test',
       id: '1',
     };
@@ -120,7 +119,7 @@ describe('ClientNats', () => {
       it('should call callback with expected arguments', () => {
         expect(
           callback.calledWith({
-            err: null,
+            err: undefined,
             response: responseMessage.response,
           }),
         ).to.be.true;
@@ -142,7 +141,7 @@ describe('ClientNats', () => {
           callback.calledWith({
             isDisposed: true,
             response: responseMessage.response,
-            err: null,
+            err: undefined,
           }),
         ).to.be.true;
       });