Describe how you would implement a user authentication flow in Flutter using an architectural pattern like Provider or BLoC.

Implementing a user authentication flow in Flutter using an architectural pattern involves combining Provider and BLoC for a robust and scalable solution. Provider can be used for dependency injection, ensuring that authentication-related dependencies are easily accessible throughout the app. BLoC can manage the authentication state, handling complex logic and transitions between authentication states such as logged in, logged out, or authentication error. Combining Provider and BLoC provides a clean and maintainable architecture for user authentication in Flutter.