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-core-utils/src/validator.js

@@ -7,13 +7,13 @@ Joi.address = () => {
     first_name: Joi.string().required(),
     last_name: Joi.string().required(),
     address_1: Joi.string().required(),
-    address_2: Joi.string().allow(""),
+    address_2: Joi.string().allow(null),
     city: Joi.string().required(),
     country_code: Joi.string().required(),
-    province: Joi.string().allow(""),
+    province: Joi.string().allow(null),
     postal_code: Joi.string().required(),
     phone: Joi.string().optional(),
-    metadata: Joi.object(),
+    metadata: Joi.object().allow(null),
   })
 }