Design a comprehensive solution for a content management system that implements the following design patterns: Factory Method, Singleton, Observer, Strategy, and Composite. For each pattern, provide a specific use case in the context of the content management system, implement the pattern in Python with appropriate docstrings and type hints, and explain how the pattern contributes to the overall system architecture. Additionally, discuss potential drawbacks of each pattern and how to mitigate them. Include unit tests for your implementations using pytest.