[BUG] The new checkout API missing order_placed event emitting

[treoden]

Describe the bug
The new checkout API does not emit the order_placed event when an order is completed. This event is crucial for downstream processes like notifications, analytics, and integrations.

To Reproduce
Steps to reproduce the behavior:

1. Go to the checkout flow using the new checkout API.
2. Complete a purchase as a user.
3. Observe backend logs or event listeners expecting order_placed.
4. See that no event is emitted upon successful order placement.

Expected behavior
After completing an order via the new checkout API, the system should emit an order_placed event to allow further processing and integrations.

Screenshots
N/A

Background (please complete the following information):

• NodeJS Version: [fill as appropriate]
• Postgres Version: [fill as appropriate]
• EverShop Version: [fill as appropriate]
• OS: [e.g. Window, Ubuntu, Mac-OS]
• Browser [e.g. Chrome, Safari]

Additional context
This event was present in the previous checkout implementation but appears to be missing in the new API version.