Replaces MongoDB support with PostgreSQL (#151)

- All schemas have been rewritten to a relational model
- All services have been rewritten to accommodate the new data model
- Adds idempotency keys to core endpoints allowing you to retry requests with no additional side effects
- Adds staged jobs to avoid putting jobs in the queue when transactions abort
- Adds atomic transactions to all methods with access to the data layer

Co-authored-by: Oliver Windall Juhl <oliver@mrbltech.com>

packages/medusa-plugin-slack-notification/src/subscribers/order.js

@@ -4,8 +4,8 @@ class OrderSubscriber {
 
     this.eventBus_ = eventBusService
 
-    this.eventBus_.subscribe("order.placed", async (order) => {
-      await this.slackService_.orderNotification(order._id)
+    this.eventBus_.subscribe("order.placed", async ({ id }) => {
+      await this.slackService_.orderNotification(id)
     })
   }
 }