Implement Spring Security for Admin and User Roles, Refactor Controllers, and Add Custom 403 Page

[Guhapriya01]

This pull request includes the following changes:

1. Spring Security Configuration:

   • Added a SecurityConfiguration class to manage security for admin and user roles.
   • Configured two separate security filter chains:
     • Admin routes (/admin/**) are restricted to users with the ADMIN role.
     • User routes (/**) are restricted to users with the USER role.
   • Integrated existing login and logout pages with Spring Security for authentication and authorization.

2. Controller Updates:

   • Refactored Admin and User controllers to align with the new security configurations.
   • Replaced previous controller-specific logic for admin access with Spring Security configurations.

3. View and Navigation Updates:

   • Modified JSP pages for admin and user interfaces to match the updated controllers and security settings.
   • Updated navigation links to reflect changes in security and routing.

4. Error Handling:

   • Added a custom 403 error page for access denial scenarios.
   • Implemented an error controller to serve the 403 error page.

Related Issues:

• Issue Use Spring Security for Admin Role Management #79

Please review and let me know if any further changes are needed.