docs: improved commerce modules [5/5] (#9592)

- Improve remaining commerce modules
- Other: add a note about using methods of the modules' main services.

www/apps/resources/app/commerce-modules/api-key/examples/page.mdx

@@ -8,6 +8,12 @@ export const metadata = {
 
 In this guide, you’ll find common examples of how you can use the API Key Module in your application.
 
+<Note>
+
+You should only use the API Key Module's main service when implementing complex customizations. For common cases, check out [available workflows instead](../../../medusa-workflows-reference/page.mdx).
+
+</Note>
+
 ## Create an API Key
 
 <CodeTabs groupId="app-type">