* feat: update DifyPluginEnv to set default for REMOTE_INSTALL_URL and add unit tests for environment configurations
- Set default value of REMOTE_INSTALL_URL to None in DifyPluginEnv.
- Introduced unit tests for various installation methods including local, remote, and serverless configurations, ensuring proper functionality without parameters and with specific settings.
* fix: update condition for install_url check in Plugin class
- Changed the condition to explicitly check for None instead of a truthy value, improving clarity and preventing potential issues with falsy values.
* apply ruff
Yeuoly