feat: add api root endpoint

src/app.ts

@@ -16,6 +16,17 @@ const app = express();
 app.use(jsonParser);
 app.use(express.urlencoded({ extended: true }));
 
+app.get('/', (_req, res) => {
+  res.json({
+    message: 'Welcome to Echo Service! Send your requests to /echo endpoint',
+    availableEndpoints: {
+      echo: '/echo',
+      health: '/health'
+    },
+    documentation: SERVICE_INFO.SOURCE_CODE
+  });
+});
+
 app.get('/health', (_req, res) => {
   const healthResponse: HealthCheckResponse = {
     status: 'healthy',

src/tests/integration/app.test.ts

@@ -1,6 +1,7 @@
 import request from 'supertest';
 
 import app from '../../app.js';
+import { SERVICE_INFO } from '../../config/constants.js';
 import * as responseUtils from '../../utils/response.js';
 
 const mockHostname = jest.fn().mockReturnValue('test-host');
@@ -22,6 +23,24 @@ describe('Echo Service Integration Tests', () => {
     process.env.NODE_ENV = originalEnv;
   });
 
+  describe('GET /', () => {
+    it('should return 200 and welcome message with available endpoints', async () => {
+      const response = await request(app)
+        .get('/')
+        .expect('Content-Type', /json/)
+        .expect(200);
+
+      expect(response.body).toEqual({
+        message: 'Welcome to Echo Service! Send your requests to /echo endpoint',
+        availableEndpoints: {
+          echo: '/echo',
+          health: '/health'
+        },
+        documentation: SERVICE_INFO.SOURCE_CODE
+      });
+    });
+  });
+
   describe('GET /health', () => {
     it('should return 200 and health status', async () => {
       const response = await request(app)