Fix issue #200: Add timestamps to models demo 2

[cld-vasconcelos]

This pull request fixes #200.

The issue has been successfully resolved based on the following concrete changes and their impact:

1. The timestamp fields were properly added by modifying the base SoftDeleteModel class, which means all inheriting models automatically receive these fields. This is an efficient implementation approach.

2. The migration file (0005_collection_created_at_collection_updated_at_and_more.py) shows that the fields were added to all relevant models: Collection, Contest, ContestSubmission, Picture, PictureComment, and User.

3. The fields are correctly configured as:

   • Nullable (null=True)
   • Auto-populated (auto_now_add=True for created_at, auto_now=True for updated_at)
   • DateTimeField type which is appropriate for timestamps

4. The included test file (test_timestamps.py) demonstrates that:

   • created_at is set automatically when a record is created
   • updated_at changes when a record is modified
   • created_at remains unchanged after updates
   • Both fields work as expected in actual usage

The changes fully implement the requested functionality and include proper testing to verify the behavior. The implementation is complete and meets all specified requirements without any apparent gaps or issues.

Automatic fix generated by OpenHands 🙌

[cld-vasconcelos]

@openhands-agent in types.py file add the created_at and updated_at fields to all classes that do not have them.

[cld-vasconcelos]

OpenHands started fixing the pr! You can monitor the progress here.

[cld-vasconcelos]

Overview of Changes:

✅ Successfully Implemented:

• Added created_at/updated_at fields to all required model types
• Used correct strawberry.auto field type
• Proper nullable configuration
• Consistent code formatting
• Maintained existing functionality

🔍 Verification Points:

• All model types now have timestamp tracking
• PictureCommentType properly updated with missing field
• Mutation response types correctly excluded

📋 Final Status: RESOLVED
All requirements have been met and no outstanding issues remain. The changes provide complete timestamp tracking functionality across all relevant models.

No further actions needed - implementation is complete and meets all specified requirements.