Booking module | Create Booking

# Create Booking Process

### User Story

As a user, I want to be able to create new booking for the shuttle. If the booking seat already exists in the shuttle, the system should display an error message indicating that the seat num already exists.

### Task

- [x] Implement Data Access Object (DAO) Layer.
- [x] Implement Service Layer.
- [x] Create JUnit Test Cases.
- [x] Ensure that the tests cases are passing.
- [ ] Write clear and concise comments in the code to explain complex logic.

### DAO:

- createBooking()

### Service:

- registerBooking()

### Junit Test:
- testRegisterBookingSuccess()
- testAlreadyExistSeatNum()

### Estimation:
- 4hrs

## Flowchart

```mermaid

graph TD;
A[Start] -->|Booking Creation| B(Validate Booking);
B -->|Invalid| C{Invalid Booking Exception};
B -->|Valid| D[Confirm Booking];
C -->|Not Available| E[Notify User];
D --> F[Payment];
F --> G[Confirmation];
E --> E|End|;

style I fill:#dfd,stroke:#333
style G fill:#fdd,stroke:#333

Start with the booking DAO method createBooking() and service method registerBooking(), then review testRegisterBookingSuccess() and testAlreadyExistSeatNum(). Identify the complex logic in those areas that still lacks comments; done means clear, concise comments are added and the existing JUnit tests continue to pass.

Written by the indexing model from the issue text.