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-fulfillment-manual/src/services/manual-fulfillment.js

@@ -36,6 +36,11 @@ class ManualFulfillmentService extends FulfillmentService {
     return Promise.resolve({})
   }
 
+  createFulfillment() {
+    // No data is being sent anywhere
+    return Promise.resolve({})
+  }
+
   cancelFulfillment() {
     return Promise.resolve({})
   }