Rule: Generate a reusable Flask authentication module with the following requirements:

1. Use Flask Blueprint to isolate auth routes (login, logout, register).
2. Implement User model with SQLAlchemy ORM:
   - Fields: id (int, primary key), username (unique), email (unique), password_hash.
3. Use secure password hashing (e.g., Werkzeug's generate_password_hash and check_password_hash).
4. Provide WTForms form classes for login and registration, with validation:
   - LoginForm: email, password.
   - RegistrationForm: username, email, password, confirm password.
5. Implement routes for:
   - /login: GET to display login form; POST to process login with validation.
   - /logout: logs out user and redirects to login page.
   - /register: GET to display registration form; POST to create new user with validation.
6. Use Flask-Login for user session management.
7. Render HTML templates stored under templates/auth/:
   - login.html
   - register.html
8. Structure the module as a Python package with:
   - __init__.py to create Blueprint instance.
   - models.py for User model.
   - forms.py for WTForms classes.
   - routes.py for route definitions.
9. Write clean, readable, and well-commented code.
10. Ensure all database interactions are via SQLAlchemy session.
11. Provide clear error handling for invalid inputs or failed logins.
12. Avoid hardcoding secrets or configurations; use config variables.
13. Make the module easily integrable by importing and registering the Blueprint in any Flask app.

Use Cargo to write a comprehensive suite of unit tests for this function