refactor: remove deprecated apis from 3rd-party deps

Replacie old and deprecated APIs from `rxjs`, `body-parser`
and NodeJS core (read this guide https://nodejs.org/en/docs/guides/buffer-constructor-deprecation).
Do notice that the later only touches test files, thus doesn't affect
production code.

integration/microservices/src/grpc-advanced/advanced.grpc.controller.ts

@@ -134,8 +134,8 @@ export class AdvancedGrpcController {
   async streamReq(messages: Observable<any>): Promise<any> {
     const s = new Subject();
     const o = s.asObservable();
-    messages.subscribe(
-      msg => {
+    messages.subscribe({
+      next: () => {
         s.next({
           id: 1,
           itemTypes: [1],
@@ -146,9 +146,8 @@ export class AdvancedGrpcController {
           },
         });
       },
-      null,
-      () => s.complete(),
-    );
+      complete: () => s.complete(),
+    });
     return o;
   }
 

integration/microservices/src/grpc/grpc.controller.ts

@@ -50,16 +50,16 @@ export class GrpcController {
   @GrpcStreamMethod('Math')
   async sumStream(messages: Observable<any>): Promise<any> {
     return new Promise<any>((resolve, reject) => {
-      messages.subscribe(
-        msg => {
+      messages.subscribe({
+        next: msg => {
           resolve({
             result: msg.data.reduce((a, b) => a + b),
           });
         },
-        err => {
+        error: err => {
           reject(err);
         },
-      );
+      });
     });
   }