[Soroban] Payment cancellation by merchant via contract call

[Xaxxoo]

Overview

Allow merchants to cancel a pending (not yet confirmed) payment by invoking the contract, which releases the escrow back to the customer if already deposited.

Tasks

• Add cancel_payment(payment_id) callable by merchant address
• Only allow cancellation in Pending state
• Refund customer if deposit already made
• Emit PaymentCancelled event
• NestJS listens to event and updates DB status
• Unit test cancellation before and after deposit

Acceptance Criteria

• Merchants can cancel pending payments on-chain
• Any deposited funds are auto-refunded on cancellation

[devoclan]

@devoclan has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

i will like to work on this

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

[drips-wave]

Congratulations, @devoclan! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @devoclan: 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

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