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/babel-preset-medusa-package/index.js

@@ -15,7 +15,10 @@ function preset(context, options = {}) {
   return {
     presets: [r(`@babel/preset-env`)],
     plugins: [
-      r(`@babel/plugin-proposal-class-properties`),
+      r(`babel-plugin-transform-typescript-metadata`),
+      r(`@babel/plugin-proposal-optional-chaining`),
+      [r(`@babel/plugin-proposal-decorators`), { legacy: true }],
+      [r(`@babel/plugin-proposal-class-properties`), { loose: true }],
       r(`@babel/plugin-transform-classes`),
       r(`@babel/plugin-transform-instanceof`),
       r(`@babel/plugin-transform-runtime`),