Refactor connection manager

This MR relies on previous MRs.

apps/connection-manager/src/__tests__/application.spec.ts

 import type { INestApplication } from '@nestjs/common';
-import type { TestingModule } from '@nestjs/testing';
 
 import { Test } from '@nestjs/testing';
 
-import AppModule from './app.module.js';
+import { Application } from '../application.js';
 
-describe('App Module', () => {
+describe('Application', () => {
   let app: INestApplication;
 
-  beforeAll(async () => {
-    const moduleFixture: TestingModule = await Test.createTestingModule({
-      imports: [AppModule],
+  beforeEach(async () => {
+    const moduleRef = await Test.createTestingModule({
+      imports: [Application],
     }).compile();
 
-    app = moduleFixture.createNestApplication();
+    app = moduleRef.createNestApplication();
     await app.init();
   });
 
-  it('should work', () => {
-    expect(true).toBe(true);
+  afterEach(async () => {
+    await app.close();
   });
 
-  afterAll(async () => {
-    await app.close();
+  it('should be defined', () => {
+    expect(app).toBeDefined();
   });
 });