### 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?
- Update chat assistant tests to use dataset.id directly in payloads
- Enhance document parsing tests with better condition checking
- Add explicit type hints and improve timeout handling
Action_7556
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### 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
### What problem does this PR solve?
- Improve concurrent test cases by using as_completed for better
reliability
- Rename variables for clarity (chunk_num -> count)
- Add new SDK API test suite for chunk management operations
- Update HTTP API tests with consistent concurrency patterns
### Type of change
- [x] Add test cases
- [x] Refactoring
