Borrow Module | Return Book Feature

# Returning Borrow Process

### User Story
As a user, I want to be able to return a book that I have borrowed from the library. When I finish reading a book, I should be able to initiate the process of returning it. The system should calculate any late fines if I return the book after the due date. After returning the book, I should receive a confirmation message indicating that the return was successful.

### 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.
- [x] Write clear and concise comments in the code to explain complex logic.

#### DAO
- returnBook()

#### Service
- returnBook()

#### Junit Test
- testValidReturnBook()
- testInvalidReturnBook()

### Estimation
- 2 hours

# Flowchart

```mermaid
graph TD
A[[Start]] --> |User Initiates Borrow Return| B[(Retrieve Borrow Details)]
B --> C([Validate Return Date])
C --> |Valid Date| D([Calculate Late Fine])
D --> E{{Service Exception}}
E --> H([Failed to Return Borrow])
C --> |Invalid Date| E
D --> |Update Borrow Record| G([Display Return Success Message])
G --> I
H --> I[[End]]

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