Build invoice payment expiry

[Kingsman-99]

Label: complexity: high
Points: 200

Description

Payers who contribute to a long-running invoice may want their funds returned if the invoice isn't fully funded within their chosen timeframe. This issue adds payer_expiry: u64 per payment — if the invoice is still pending after payer_expiry, that specific payer can call reclaim_expired_payment() to retrieve their contribution.

Technical Context

Involves types.rs (add expiry: u64 to Payment) and lib.rs. Update pay() to accept optional payer_expiry: u64. Add reclaim_expired_payment(env, invoice_id, payer) requiring payer auth, asserting env.ledger().timestamp() > payment.expiry, transferring payer's total back, removing their payments, updating invoice.funded.

Acceptance Criteria

• pay() accepts optional payer_expiry timestamp
• reclaim_expired_payment() requires payer auth
• Panics with "payment not expired" before expiry timestamp
• Payer receives full contributed amount back after expiry
• invoice.funded decremented correctly after reclaim
• All existing cargo tests pass
• cargo clippy passes with zero warnings

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[Henrichy]

@Henrichy has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

My name is Henry Nzekwe, a Full Stack Developer with experience in Rust, smart contracts, backend systems, and financial application development. I am interested in implementing the invoice payment expiry functionality for the Split Contracts project.

I can extend the Payment structure to support payer_expiry timestamps, update the pay() function to accept an optional expiry parameter, and implement reclaim_expired_payment() with proper payer authentication and validation checks. The solution will ensure contributors can safely reclaim funds from invoices that remain unfunded beyond their chosen expiry period while maintaining contract integrity.

I will carefully handle payment aggregation, fund transfers, invoice.funded adjustments, and storage updates to prevent inconsistencies. In addition, I will add comprehensive test coverage for expiry validation, successful refunds, authorization requirements, and edge cases, ensuring all cargo tests and clippy checks pass without warnings.

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

[levi0005]

@levi0005 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer, i would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @levi0005 to this issue.

[drips-wave]

Congratulations, @levi0005! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @levi0005: 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.

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