docs(ack-pay): document receipt evidence metadata

[EfeDurmaz16]

Summary

• Document optional ACK-Pay receipt evidence metadata for policy, mandate, execution, and settlement references
• Clarify that receipt metadata is non-normative application evidence and should not carry secrets or raw payment credentials
• Add a verification round-trip test proving receipt metadata survives signing, JWT parsing, and receipt verification

Fixes #92

Verification

• pnpm run build
• pnpm --filter ./packages/ack-pay exec vitest run src/verify-payment-receipt.test.ts src/create-payment-receipt.test.ts
• pnpm --filter ./packages/ack-pay check:types
• pnpm exec oxfmt --check docs/ack-pay/receipt-verification.mdx packages/ack-pay/src/verify-payment-receipt.test.ts
• git diff --check

Summary by CodeRabbit

• Documentation

  • Added Receipt Evidence Metadata section documenting metadata usage as an optional extension point in receipts, including stability guarantees, non-normative constraints, and example JSON structure.

• Tests

  • Added test case verifying metadata preservation during payment receipt verification.

[coderabbitai]

Walkthrough

This PR documents optional receipt evidence metadata as a non-normative extension point in ACK payment receipts, allowing implementers to link receipts to policy, mandate, and execution references without modifying the core credential format. Includes test setup improvements and a new test confirming metadata preservation through signing and verification.

Changes

Receipt Evidence Metadata Feature

Layer / File(s)	Summary
Receipt metadata documentation docs/ack-pay/receipt-verification.mdx	Adds "Receipt Evidence Metadata" section defining credentialSubject.metadata as an optional, verifier-specific extension point for evidence and reference hashes (policy, mandate, execution, settlement). Clarifies that core fields remain stable, metadata is non-normative, and secrets must be excluded. Includes JSON example.
Test setup refactoring for keypair and payment request reuse packages/ack-pay/src/verify-payment-receipt.test.ts	Introduces outer-scoped receiptIssuerKeypair initialized in beforeEach for reuse across tests. Refactors payment-request creation to store the result, extract paymentRequestToken, and use the generated payment option id when building unsigned receipts.
Metadata preservation test packages/ack-pay/src/verify-payment-receipt.test.ts	Adds test case that creates a receipt with metadata, signs it into a JWT, verifies it via verifyPaymentReceipt, and confirms the returned credential preserves the metadata under credentialSubject.metadata.

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🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: documenting receipt evidence metadata for ACK-Pay, which is the primary focus of both the documentation additions and test modifications.
Linked Issues check	✅ Passed	The PR fully addresses issue #92 requirements: documentation of optional receipt metadata fields is added, a test demonstrating metadata survives signing/parsing/verification is included, and core schema fields remain unchanged.
Out of Scope Changes check	✅ Passed	All changes directly support the stated objective of documenting receipt evidence metadata without modifying core receipt schema or verifier semantics; no out-of-scope changes detected.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (2)

packages/ack-pay/src/verify-payment-receipt.test.ts (2)

117-120: ⚡ Quick win

Use derived paymentOptionId instead of a hardcoded literal.

This test now bypasses the setup’s dynamic fixture derivation by pinning "test-payment-option-id". Reusing a derived id keeps the round-trip test resilient to fixture changes.

♻️ Proposed change

   const receiptWithMetadata = createPaymentReceipt({
       paymentRequestToken,
-      paymentOptionId: "test-payment-option-id",
+      paymentOptionId: unsignedReceipt.credentialSubject.paymentOptionId,
       issuer: receiptIssuerDid,

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/ack-pay/src/verify-payment-receipt.test.ts` around lines 117 - 120,
The test uses a hardcoded paymentOptionId string when calling
createPaymentReceipt; replace that literal with the dynamically derived id from
the test fixture/setup (the variable used earlier in the test setup, e.g.
paymentOption.id or derivedPaymentOptionId) so createPaymentReceipt({
paymentRequestToken, paymentOptionId: <use-derived-id>, issuer: receiptIssuerDid
}) uses the actual fixture-derived id and preserves round-trip resilience.

---

105-105: ⚡ Quick win

Rename the test to match the required assertive naming pattern.

Use one of the approved prefixes (e.g., returns) for consistency with test conventions.

✏️ Proposed rename

-  it("preserves receipt metadata through JWT verification", async () => {
+  it("returns receipt metadata through JWT verification", async () => {

As per coding guidelines, "Use assertive test names with patterns: it(\"creates...\") , it(\"throws...\") , it(\"requires...\") , it(\"returns...\")".

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/ack-pay/src/verify-payment-receipt.test.ts` at line 105, The test
currently named "preserves receipt metadata through JWT verification" should be
renamed to follow the assertive naming convention (use an approved prefix such
as "returns"); update the it(...) description string in the test definition so
it begins with "returns" (for example: "returns receipt metadata after JWT
verification") to match the project's required assertive test-name pattern and
keep the same test body and assertions in verify-payment-receipt.test.ts.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@packages/ack-pay/src/verify-payment-receipt.test.ts`:
- Around line 117-120: The test uses a hardcoded paymentOptionId string when
calling createPaymentReceipt; replace that literal with the dynamically derived
id from the test fixture/setup (the variable used earlier in the test setup,
e.g. paymentOption.id or derivedPaymentOptionId) so createPaymentReceipt({
paymentRequestToken, paymentOptionId: <use-derived-id>, issuer: receiptIssuerDid
}) uses the actual fixture-derived id and preserves round-trip resilience.
- Line 105: The test currently named "preserves receipt metadata through JWT
verification" should be renamed to follow the assertive naming convention (use
an approved prefix such as "returns"); update the it(...) description string in
the test definition so it begins with "returns" (for example: "returns receipt
metadata after JWT verification") to match the project's required assertive
test-name pattern and keep the same test body and assertions in
verify-payment-receipt.test.ts.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 5eca1f7f-3435-4c22-9f47-c11fee350a36

📥 Commits

Reviewing files that changed from the base of the PR and between 6f65936 and d9552be.

📒 Files selected for processing (2)

• docs/ack-pay/receipt-verification.mdx
• packages/ack-pay/src/verify-payment-receipt.test.ts