### What problem does this PR solve?
- Add comprehensive test suite for chunk operations including:
- Test files for create, list, retrieve, update, and delete chunks
- Authorization tests
- Batch operations tests
- Update test configurations and common utilities
- Validate `important_kwd` and `question_kwd` fields are lists in
chunk_app.py
- Reorganize imports and clean up duplicate code
### Type of change
- [x] Add test cases
### 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
