Fix issue #188: Create winners view V3

[cld-vasconcelos]

This pull request fixes #188.

The issue has been successfully resolved based on the following implemented changes and their effects:

1. The code implements the exact data structure requested in the original JSON specification through new GraphQL types (ContestWinnersType, ContestWinnerType, WinnerSubmissionType) that match the required schema.

2. The query implementation in contest_winners correctly:

• Filters contests to only those with winners using exclude(winners=None)
• Orders results by voting_draw_end as required
• Retrieves all necessary data including contest details, winner information, and submission details with vote counts
• Properly formats the voting_draw_end date as an ISO string

3. The comprehensive test suite verifies:

• Correct data structure and field population
• Proper handling of multiple winners per contest
• Accurate vote counting
• Correct date-based ordering
• All required fields are present and properly formatted

4. The implementation handles all edge cases including:

• Multiple winners per contest
• Vote counting for submissions
• Proper relationship mapping between contests, winners, and their submissions
• Null date handling

The code changes directly fulfill all requirements from the original issue description and the test suite provides evidence that the implementation works as intended. The data structure, ordering, and all required fields are present and functioning correctly.

Automatic fix generated by OpenHands 🙌