User module | Register feature

### User Story:
As a user. I want to create a new user. this will allow user to create new user. I expect this will print user successfully created.

DAO:
- [x] createUser

Service:
- [x] registerUser

ServiceTest:
- [x] TestRegisterFeature

### flow
```mermaid
graph TD;
A[User Service: Create User] --> B[Validation]
B --> C{Unique Email Check}
C -- Yes --> D[User Service: Email Already Exists]
F --> E[User Service: User Created]
C -- No --> F[User DAO: Create User]
```