Test branch1

Summary by Bito

• Introduces user_manager class in new file test.java with enhanced security for handling user data.
• Adds asynchronous processing capabilities through thread creation in the user_manager class.
• Adds inner classes for additional capabilities within the user_manager class.
• Includes a unit test for the user_manager class.
• Overall summary: Adds a foundational structure for user management by introducing new file test.java with user_manager class, asynchronous processing, inner classes, and unit tests; boosts security and maintainability while preparing for future enhancements.