[Backend] Admin Competition Management - Cancel Competition

[Olowodarey]

📋 Issue

No way for admins to cancel competitions.

Endpoint: DELETE /admin/competitions/:id (NEW)

Required Implementation

• Add is_cancelled field to Competition entity
• Refund participants if applicable
• Send notifications to participants

Tasks

• Add is_cancelled field to Competition entity
• Create migration
• Implement cancel endpoint
• Handle participant refunds
• Send cancellation notifications
• Write tests

Access: Admin only

[Samaro1]

@Samaro1 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

gm gm boss, I would love to work on this issue, I will provide a satisfactory and efficient PR in 6 hours tops

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Samaro1 to this issue.

[drips-wave]

Congratulations, @Samaro1! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @Samaro1: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊

[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @Samaro1 as part of the Stellar Wave Program's 3rd Wave 🥳

Moderator's reason: [Auto-assessed] The contributor successfully implemented all requirements for the competition cancellation feature, including the entity field, database migration, admin endpoint, refund logic, and notifications. The PR #521 was reviewed and merged by the maintainers, and the issue is now closed.

😎 @Samaro1: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.

ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.