MULTI_USER_IMPLEMENTATION.md

Multi-User System Implementation

Changes Made

The Subscription Tracker has been converted from a single-user to a multi-user system with role-based access control.

Key Features

1. User Roles:

   • Standard Users: Can only manage their own subscriptions and settings
   • Admin Users: Can manage all users, create new users, and access admin settings

2. User Management:

   • Registration is disabled for public users
   • Only admins can create new users
   • Admins can modify user roles, passwords, and delete users (with restrictions)

3. Security:

   • Admins cannot delete themselves while logged in
   • There must always be at least one admin user
   • The last admin cannot have their admin role removed

Implementation Details

Database Changes

• User model already had is_admin field
• Added cascade delete relationships for UserSettings and Subscriptions
• Each user has isolated subscriptions and settings

Routes Added

• /admin/users - List all users (admin only)
• /admin/users/add - Add new user (admin only)
• /admin/users/edit/<id> - Edit user (admin only)
• /admin/users/delete/<id> - Delete user (admin only)

Templates Added

• admin_users.html - User management dashboard
• admin_add_user.html - Add user form
• admin_edit_user.html - Edit user form

Forms Added

• AdminUserForm - For creating new users
• AdminEditUserForm - For editing existing users

Navigation Changes

• Removed registration link from login page
• Added "Admin Settings" menu item for admin users
• Admin settings accessible via Settings dropdown

Admin User Creation

The system automatically creates a default admin user if no admin exists:

• Username: admin
• Password: changeme
• This only happens if there are no existing admin users

User Isolation

• Each user has their own subscriptions and settings
• Users cannot access other users' data
• All existing functionality (dashboard, analytics, etc.) works per-user
• Currency conversion, notifications, and other features work independently per user

Admin Capabilities

Admin users can:

• View all users in the system
• Create new users (both standard and admin)
• Edit user details (username, email, password, role)
• Delete users (with restrictions)
• See user statistics (subscription counts)

Restrictions

• Admins cannot delete themselves while logged in
• Cannot delete the last admin user
• Cannot remove admin role from the last admin
• Deleting a user also deletes all their subscriptions and settings

Migration Notes

• Existing users will retain their data
• If upgrading from single-user, the existing admin user will remain as admin
• No data migration needed - all existing subscriptions belong to existing users

Security Considerations

• All admin routes check for admin privileges
• User isolation is enforced at the database query level
• Proper error handling prevents information leakage
• Form validation prevents privilege escalation

This implementation provides a clean separation between users while maintaining the existing functionality for each individual user.