Optional on-chain index: payer to stream ids (capped)

[greatest0fallt1me]

Description

Bounded Vec of stream IDs per payer for simple UIs without indexer (cap e.g. 50).

Requirements and context

• Document overflow policy when cap exceeded.
• Gas implications.

Suggested execution

• Fork the repository and create a branch (example below).
• Implement the changes in the StreamPay-Contracts Soroban crate (streampay-contracts).
• Keep the contract secure, tested, and documented; prefer small, reviewable diffs.

git checkout -b feature/payer-stream-index-capped

Implementation targets

• lib.rs storage.
• Tests at cap.

Tests and validation

• Add or extend contract tests for this scope.

• Cover edge cases; paste summarized test output and security notes in the PR.

• Run cargo test in StreamPay-Contracts.

• Cover edge cases; capture test output and short security notes in the PR description.

Guidelines

• Target minimum 95% test coverage for touched contract code (or justify gaps explicitly).
• Clear documentation (rustdoc / project docs as specified).
• Timeframe: 96 hours from assignment.

Example commit message

feat(contracts): capped on-chain payer to stream id index

[rohan911438]

@rohan911438 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hi, I’d like to work on this issue. I understand the requirements and can start immediately. I’ll ensure a clean, tested implementation and a quick turnaround. Kindly assign this to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @rohan911438 to this issue.

[drips-wave]

Congratulations, @rohan911438! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @rohan911438: 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 🌊