Refactor tests for Postgres activities and improve error handling
- Updated test_postgres.py to enhance the testing of load_custom_query method, including cases for None data and date conversion.
- Refactored repeat_last_prediction tests to use mocks for SQLAlchemy session execution.
- Added tests for export_data_to_postgres method, covering both success and error scenarios.
- Improved the initialization tests for Activities class to ensure proper instantiation of dependencies.
- Enhanced test coverage for OPC repository connection validation.
- Updated tests for prediction workflows to streamline input handling and improve clarity.
- Introduced tests for connectors configuration to validate environment variable handling for MLFlow, OPC, and Postgres.
- Added tests for logger utility to ensure default settings are correctly applied.
