Akka Http Service

Routes

1. POST /register - Register a new user
2. POST /login - Login user
3. POST /logout - Logout user
4. GET /books - Get all books
5. GET /books/:id - Get book
6. POST /books - Create book (admin permission required)
7. PUT /books/:id - Update book (admin permission required)
8. DELETE /books/:id - Delete book (admin permission required)
9. GET /orders - Get orders (admin gets all orders, user gets just personal orders)
10. POST /orders - Create order (No need negative quantity check)