docs: Add Services reference (#1548)

docs/content/advanced/backend/services/create-service.md

@@ -102,4 +102,5 @@ constructor({ helloService, eventBusService }) {
 
 ## What’s Next 🚀
 
+- Check out the [Services Reference](/references/services/classes/AuthService) to see a list of all services in Medusa.
 - [Learn How to Create an Endpoint.](/advanced/backend/endpoints/add-storefront)