bug: atomic compensation + consistent settlement rounding in RFQ execution saga (COG-GTM Execution Saga)

[devin-ai-integration]

Summary

Fixes a bug where a counterparty credit-check failure mid-saga left the bond's available notional understated, and a separate inconsistent-rounding bug in settlement math.

Root cause (compensation). RFQExecutionSaga.executeRfq deducts bond notional, then deducts counterparty credit. When deductCredit throws InsufficientCreditException, the saga relied solely on @Transactional rollback and never reversed the in-flight bond.deductNotional(...) mutation. When the saga's @Transactional joins an outer/shared persistence context (the production path), the managed Bond is left dirty with the deduction, so the bond's availableNotional stays reduced and subsequent quotes are wrongly rejected. The old code comment ("No need for saga compensation…") was incorrect.

Root cause (rounding). executionPrice was persisted and debited verbatim, with no currency-scale normalization → off-by-a-cent settlement values.

Fix:

settlementAmount = executionPrice.setScale(2, HALF_EVEN)   // consistent currency scale
bond.deductNotional(notional)
try {
    counterparty.deductCredit(settlementAmount)
} catch (InsufficientCreditException e) {
    bond.addNotional(notional)   // explicit compensation
    throw e
}
save Rfq(..., settlementAmount)

Change is scoped to RFQExecutionSaga; no unrelated refactors.

Reproduction & verification

Added a failing repro first (creditCheckFailure_rollsBackBondNotionalDeduction): before the fix it observed availableNotional understated by the trade notional (50000000.00 → 49000000.00) after the credit check failed. It now passes.

New JUnit 5 tests in RFQExecutionSagaTest:

• (a) credit-check fails after notional deduction → bond notional restored, credit unchanged
• (b) successful execution still debits bond notional and counterparty credit correctly
• (c) HALF_EVEN rounding boundary cases (.005→.00, .015→.02, .025→.02)
• notional-check failure leaves both aggregates unchanged

Test output

Tests run: 6, Failures: 0, Errors: 0, Skipped: 0 - RFQExecutionSagaTest
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0 - IntegrationTest
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

(mvn test, Java 11)

Link to Devin session: https://app.devin.ai/sessions/78af6ddcdc804c8088d3d9a1e22b213a
Requested by: @achalc

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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