feat: Add CI configuration, testing setup, and initial test cases (#130)

*  feat: Add CI configuration, testing setup, and initial test cases

*  feat: Add 'dummy' vector store mode for testing and development

*  feat: Update CI configuration and remove dummy vector store mode

*  feat: Improve error handling for invalid mode in store_factory.py

*  feat: Refactor project structure and implement new vector store services

*  feat: Add request validation error handling and implement main application logic

*  fix: Ensure newline at end of file in main.py

*  feat: Implement main application logic with FastAPI and document handling endpoints

*  refactor: Clean up and organize imports in main.py; enhance document routes with improved error handling

*  refactor: Streamline health check logic and improve document deletion handling; add health utility module

*  feat: Add initial test suite for application components; include tests for configuration, database, document loading, health checks, middleware, and models

*  test: Add configuration for testing environment and implement dummy vector store for unit tests

*  test: Add configuration for testing environment and implement dummy vector store for unit tests

*  refactor: Remove redundant health check test; streamline test suite

*  feat: Implement asynchronous vector store classes for PostgreSQL and MongoDB; enhance document handling and retrieval