Adding a little CE / S3 mapping hint

Signed-off-by: Matthias Wessendorf <mwessend@redhat.com>

blog/docs/articles/aws_to_func_migration.md

@@ -73,6 +73,11 @@ Note that this complete program contains only one function, which is focused on
 
 Looking closer at the signature of the `Handle` function, we see the standard `Context` API and an `Event` type. This is no vendor specific import. It references the Golang SDK for [CNCF CloudEvents](https://www.cncf.io/projects/cloudevents/){:target="_blank"}, which is a specification for describing event data in a common way.
 
+!!! note
+
+    CNCF CloudEvents allows a generic and independent approach for receiving events. In the [previous post](/blog/articles/consuming_s3_data_with_knative){:target="_blank"} we covered the AWS S3 related mapping for CloudEvents, such as that `subject` is the name of the file, similar to the S3 Object Key or the `source` is containing the actual name of the S3 bucket. The raw date of the record itself is available on the `data` attribute of the passed in CloudEvent.
+
+
 ## Knative CLI for Smooth Development and Deployment
 
 The Knative Function project does not only offer a vendor-neutral approach for creating serverless functions, it also comes with a handy CLI that assists with the creation of the Linux container image and the deployment to a Kubernetes cluster.  This is covered in the [previous blog post](/blog/articles/consuming_s3_data_with_knative){:target="_blank"}. It also allows you to test and run the function locally by  invoking: