Vault: `request_id` event encoding (empty symbol convention)

[greatest0fallt1me]

Description

Document and test how optional request_id is represented in deduct event topics so indexers parse consistently.

Requirements and context

• Avoid breaking schema changes without an explicit version/migration note.
• Align EVENT_SCHEMA.md with implementation.

Suggested execution

• Fork the repo and create a branch: git checkout -b docs/vault-request-id-events
• Implement changes in the Callora-Contracts Soroban workspace (contracts/*/src/).
• Run cargo fmt, cargo clippy --all-targets --all-features -- -D warnings, and cargo test from the workspace root.
• For WASM release builds: cargo build --target wasm32-unknown-unknown --release -p callora-vault (adjust -p if the crate name differs).

Deliverables

• EVENT_SCHEMA.md + test.rs (where the Soroban test harness allows assertions).
• UPGRADE.md note if behavior changes.

Test and commit

• Run tests and ./scripts/coverage.sh (or cargo tarpaulin per tarpaulin.toml).
• Cover edge cases; include summarized test output and brief security notes in the PR description.

Example commit message

docs(vault): clarify request_id event encoding

Guidelines

• Minimum 95% line coverage for touched crates (workspace policy).
• Clear documentation (Rust /// on public items where applicable; repo markdown as needed).
• Timeframe: 96 hours from assignment unless agreed otherwise.

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[Kanasjnr]

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

I’d love to take this on. I’ve already contributed to this repo with merged PRs, so I’m familiar with the vault contract structure and event patterns.

For this, I’ll trace how request_id is currently emitted in deduct events, verify how the optional value is encoded (including the empty symbol convention), and ensure it’s consistent and unambiguous for indexers. I’ll then update EVENT_SCHEMA.md to reflect the exact encoding, aligned strictly with the implementation.

On the testing side, I’ll extend the Soroban test harness to assert event topics for both cases (with and without request_id), covering edge cases to ensure indexers can reliably parse them. If any behavior needs clarification or adjustment, I’ll document it clearly and add an UPGRADE.md note only if required to avoid breaking expectations.

Kindly assign this to me can start right away.

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

🧑‍💻 @Kanasjnr: 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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