Add user GET endpoint, schemas, and security middlewares

Introduces GET /users/:id endpoint with validation schema, adds tests for user and register routes, and applies security middlewares (helmet, hpp, cors) to the server. Also adds ESLint configuration and updates logger with linting comments.

tests/register.rest

@@ -0,0 +1,8 @@
+POST http://localhost:3000/register HTTP/1.1
+Content-Type: application/json
+
+{
+    "email": "johndoe@exemple.com",
+    "username": "johndoe",
+    "password": "Password123"
+}

tests/users/id.rest

@@ -0,0 +1,2 @@
+GET http://localhost:3000/users/johndoe HTTP/1.1
+authorization: Bearer token