### What problem does this PR solve?
- Move common constants (HOST_ADDRESS, INVALID_API_TOKEN, etc.) to
configs.py
- Update test imports to use centralized configs
- Clean up duplicate constant definitions across test files
This improves maintainability by centralizing configuration.
### Type of change
- [x] Refactoring test case
### What problem does this PR solve?
- Rename `api_key` fixture to `HttpApiAuth` across all test files
- Update all dependent fixtures and test cases to use new naming
- Maintain same functionality while improving naming clarity
The rename better reflects the fixture's purpose as an HTTP API
authentication helper rather than just an API key.
### Type of change
- [x] Refactoring
### What problem does this PR solve?
- Consolidate HTTP API test fixtures using batch operations
(batch_add_chunks, batch_create_chat_assistants)
- Fix fixture initialization order in clear_session_with_chat_assistants
- Add new SDK API test suite for session management
(create/delete/list/update)
### Type of change
- [x] Add test cases
- [x] Refactoring
### What problem does this PR solve?
- Implement new SDK API test cases for chat assistant CRUD operations
- Enhance HTTP API concurrent tests to use as_completed for better
reliability
### Type of change
- [x] Add test cases
- [x] Refactoring
