User Module | Login Feature #2

### DAO:
- [ ] isLogin

### Service:
- [ ] loginUser

### Service Tests
TestLoginFeature

- [ ] testLoginSuccess
- [ ] testLoginFail

### FlowChart
```mermaid
A[Start]
B[Display Login Form]
C[User Enters Email and Password]
D[Validate Input]
E{Validation Successful?}
F[Check Credentials]
G{Credentials Valid?}
H[Redirect to Product Page]
I[Show Error Message]
J[End]
end
A --> B
B --> C
C --> D
D --> E
E -- Yes --> F
F --> G
G -- Yes --> H
G -- No --> I
I --> B
H --> J
E -- No --> I
F --> I

```