Course Module | Read Feature

# Course Read Process

### User Flow

- When a user provides a valid userID, the system successfully retrieves and displays a list of courses associated with that userID.
- When a user provides an invalid userID, the system responds with an "Invalid" message, indicating that no courses were found for that userID.

### Task

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

### DAO
- readCourse()

### Service
- listCourse()

### Service Test
TestReadCourseFeature
- testReadCourseSuccess()
- testReadCourseFailure()

### Estimation
- 1 hour

# Flowchart

```mermaid
flowchart TD
A[Start]
B[User Requests to View Courses]
C[Validate UserID]
D{Validation Successful?}
E[Retrieve Course List]
F[Display Course List]
G[Display Validation Error]
H[End]

A --> B
B --> C
C --> D
D -- Yes --> E
E --> F
D -- No --> G
G --> H
F --> H
```