chore: add cross-link rest api setup and auth (#8468)

Author: soberm

src/pages/[platform]/build-a-backend/add-aws-services/rest-api/set-up-rest-api/index.mdx

@@ -171,6 +171,12 @@ backend.addOutput({
 });
 ```
 
+<Callout info="true">
+
+**Frontend Authorization Configuration**: After setting up your REST API, you'll also need to configure authorization in your frontend application. See the [REST API Authorization guide](/[platform]/build-a-backend/add-aws-services/rest-api/customize-authz/) for details on configuring IAM, Cognito User Pool, API Key, or custom authorization headers.
+
+</Callout>
+
 ## Install Amplify Libraries
 
 <InlineFilter filters={['javascript', "angular", "react", "vue", "react-native", "nextjs"]}>