dev/issues-10

[luk384090-cloud]

Summary

This PR contains two changes:

1. Refactor Assistants API imports to lazy loading (Fixes #207)

The dashscope.assistants / dashscope.threads modules have been marked as deprecated, but previously a plain import dashscope would unconditionally import these modules, causing all users to see DeprecationWarning even if they never used the Assistants API.

Changes: Removed static imports of these modules from __init__.py and switched to PEP 562 __getattr__ mechanism for on-demand loading. Import and deprecation warnings are only triggered when names like dashscope.Messages, dashscope.Runs are actually accessed.

• Added _DEPRECATED_LAZY_IMPORTS mapping table and __getattr__ / __dir__ implementation
• Added test_import_deprecation.py unit tests to cover lazy loading behavior

2. Fix Encryption using global api_key

The Encryption class previously hardcoded dashscope.base_http_api_url and dashscope.api_key global variables, causing base_url / api_key passed as function parameters to be ignored in encryption scenarios.

Changes: Added optional base_url and api_key parameters to Encryption.__init__, and api_request_factory now passes the current call's credentials when creating instances.