fix: correct order total display in notification emails ($149.99 showing as $1.50)

[devin-ai-integration]

Summary

Order confirmation notification emails were displaying wrong totals after the microservice decomposition — a $149.99 order showed as $1.50 in the email preview.

Root cause: FormatCurrency() in NotificationRenderer.cs divided the amount by 100, assuming OrderPlacedEvent.TotalAmount was transmitted in cents. However, the OrderPlacedEvent contract defines TotalAmount as a decimal already representing dollars (e.g. 149.99). The erroneous / 100m division turned 149.99 into 1.4999, which then displayed as $1.50.

Fix: Removed the / 100m division and corrected the misleading comment.

Before (total shows ¤1.50):

After (total shows ¤149.99):

Note: The ¤ currency symbol in screenshots is due to the test server's locale; in production with an appropriate locale this renders as $.

Review & Testing Checklist for Human

• Verify all producers of OrderPlacedEvent send TotalAmount in dollars, not cents — if any upstream service (e.g., Order service) actually sends cents, this fix would break that path. Check the Order service's event publishing code.
• Check for the same bug in other services — other microservices that consume monetary amounts may have copied the same incorrect cents assumption during the decomposition.
• Test end-to-end: Run the notification service locally, POST {"orderId": "11111111-1111-1111-1111-111111111111", "customerId": "22222222-2222-2222-2222-222222222222", "totalAmount": 149.99, "placedAt": "2026-03-17T12:00:00Z"} to http://localhost:5005/api/notification/events/order-placed, and confirm the preview shows $149.99. Also test with edge cases like 0.01, 999999.99, and 0.

Notes

• FormatCurrency is private static and only called within NotificationRenderer, so the blast radius of this change is limited to notification email rendering.
• ToString("C2") relies on the server's current culture for the currency symbol — this is a pre-existing behavior, not introduced by this PR.
• No existing unit tests cover FormatCurrency; consider adding one to prevent regression.

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/4f9482b9dc0f4d579b44ddce90e737c0

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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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