Backend: APIs and Data Models for Group Trip Planning

[ajmaluk]

Develop the core backend logic for trip planning:

• Create data models representing group trips, travelers, and invitations
• Build APIs to manage group formation, trip requests, joining/quitting groups, and itinerary modifications
• Ensure robust error handling and security measures for user data

Please provide specifics for:
• Required trip/group data fields
• API endpoints and behaviors
• Matching logic criteria