### 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?
- 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
