- Replaced standard log package with log/slog in httpclient, nginx manager, sync service, updater, and other components for structured logging.
- Introduced environment variable `LOG_LEVEL` to control logging levels (debug, info, warn, error).
- Updated documentation to reflect changes in logging configuration and requirements.
- Added a new logging setup function in the ats_agent internal package to initialize the slog logger.
- Updated all instances of "nginx" to "openresty" in log messages, error messages, and comments.
- Changed paths and Docker image names to reflect OpenResty usage.
- Modified test cases to align with OpenResty commands and configurations.
- Adjusted documentation to replace Nginx mentions with OpenResty, including setup instructions and configuration details.
- Ensured that version detection and runtime commands are consistent with OpenResty.
ryan