test: expand stellarRpcFailure Horizon result-code coverage

[samueloyibodevv]

Overview

This PR expands src/lib/stellarRpcFailure.test.ts to comprehensively cover Horizon extras.result_codes classification for transaction- and operation-level failures. It verifies tx_bad_seq, tx_insufficient_fee, op_no_destination, and op_underfunded, confirms shouldRetry behavior for each classified failure, and adds security assertions to ensure raw upstream messages never leak through classified output.

Related Issue

Closes #349

Changes

⚙️ Stellar Result-Code Classification Coverage

• [MODIFY] src/lib/stellarRpcFailure.test.ts
• Added deterministic fixtures for Horizon extras.result_codes payloads.
• Added explicit coverage for tx_bad_seq and tx_insufficient_fee mapping to TX_RESULT_CODE.
• Added explicit coverage for op_no_destination and op_underfunded mapping to OP_RESULT_CODE.
• Added assertions for shouldRetry on tx/op result-code classifications.
• Added coverage for operation-code precedence over transaction codes.
• Added UNKNOWN fallback coverage for unrecognized and nested unsupported shapes.
• Added edge-case coverage for missing extras, non-Error objects, and null/undefined input.

🔒 Sanitization And Security

• [MODIFY] src/lib/stellarRpcFailure.ts
• Hardened sanitizeError() so raw upstream message text is replaced with UPSTREAM_MESSAGE_REDACTED.
• Preserved a narrow diagnostic shape without leaking Horizon error strings across trust boundaries.
• Removed duplicate type/enum declarations to keep the classifier easier to review.

🧪 Related Test Alignment

• [MODIFY] src/routes/payouts.test.ts

• Updated existing assertions to match the classifier’s structured return shape.

• Added security checks confirming redacted classified output is not the raw upstream object.

• [MODIFY] src/__tests__/stellarRpcFailure.integration.test.ts

• Updated the logger mock to include .child().

• Aligned the long-message sanitization expectation with the redacted behavior.

📘 Documentation

• [MODIFY] docs/payouts-stellar-result-codes-retry-storms.md
• Documented the expanded Horizon result-code coverage and the message-redaction security guarantee.

Verification Results

Acceptance Criteria	Status
Covers tx_bad_seq classification	✅
Covers tx_insufficient_fee classification	✅
Covers op_no_destination classification	✅
Covers op_underfunded classification	✅
Asserts shouldRetry for tx/op result-code failures	✅
Asserts UNKNOWN fallback for unrecognized shapes	✅
Asserts raw upstream messages do not leak	✅
Targeted classifier-related tests pass	✅

Screenshots

✅ Targeted test run

A screenshot of:

npm test -- --runInBand src/lib/stellarRpcFailure.test.ts src/routes/payouts.test.ts

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