Fix #19: add user registration endpoint and security configuration

[Kalyanburri123]

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Fixes #19

Description

This PR adds the missing user registration functionality to the login-service.

Changes

• Implemented POST api/login/users endpoint
• Added user creation logic with validation and password encryption
• Integrated JWT-based authentication for secured endpoints
• Updated Spring Security configuration to allow public access to auth and register endpoints
• Added global exception handling using @ControllerAdvice

Testing

• Tested registration and login flows using Postman
• Verified JWT-protected endpoints by passing Bearer token
• Confirmed user persistence in MySQL database

Notes

• No breaking changes introduced
• Environment-specific configurations kept local

[Manoj-14]

please raise the PR for stage branch