Updating the lambda-trigger mdx with an example (#8008)

* Updating the lambda-trigger mdx with an example

* Update src/pages/[platform]/build-a-backend/storage/lambda-triggers/index.mdx

* Update src/pages/[platform]/build-a-backend/storage/lambda-triggers/index.mdx

---------

Co-authored-by: Brandon Watson <blwatson@kompartners.com>
Co-authored-by: josef <josef.aidt@gmail.com>

Author: 3 people

src/pages/[platform]/build-a-backend/storage/lambda-triggers/index.mdx

@@ -76,3 +76,35 @@ export const handler: S3Handler = async (event) => {
 </Callout>
 
 Now, when you deploy your backend, these functions will be invoked whenever an object is uploaded or deleted from the bucket.
+
+## More Advanced Triggers
+
+The example listed above demonstrates what is exposed directly in your `storage` definition. Specifically, the use of the `triggers` option when you use `defineStorage`. This method is for simple triggers that always execute on file uploads or file deletions. There are no additional modifications you can make to the triggers defined in this way.
+
+If you want the ability to do something more than simply handle the events `onUpload` and `onDelete` you will have to use `.addEventNotification` in your `backend.ts`. If you use this method, the `triggers` section in your `storage/resource.ts` file should be removed.
+
+Here is an example of how you can add a Lambda trigger for an S3 object PUT event. This trigger will execute when a file that has been uploaded to the bucket defined in your `storage/resource.ts` has a matching prefix and suffix as that listed in the function input of `addEventNotification`.
+
+```ts title="amplify/backend.ts"
+import { EventType } from 'aws-cdk-lib/aws-s3';
+import { LambdaDestination } from 'aws-cdk-lib/aws-s3-notifications';
+import { defineBackend } from '@aws-amplify/backend';
+import { storage } from './storage/resource';
+import { yourLambda } from './functions/yourLambda/resource';
+
+const backend = defineBackend({
+  storage,
+  yourLambda,
+});
+
+backend.storage.resources.bucket.addEventNotification(
+	EventType.OBJECT_CREATED_PUT,
+	new LambdaDestination(backend.yourLambda.resources.lambda),
+	{
+		prefix: 'protected/uploads/',
+		suffix: '-uploadManifest.json',
+	}
+);
+```
+
+It's important to note that using this methodology does not require any changes your lambda function. This modification on your `backend.ts` file will create a new `AWS CloudFormation handler for "Custom::S3BucketNotifications" resources (@aws-cdk/aws-s3)` that specifically handles checking the prefix and suffix.