update security custom header

Hi,

This is a use case which could be solved using Lambda@Edge. The blog post How to enhance Amazon CloudFront origin security with AWS WAF and AWS Secrets Manager demonstrates a similar scenario, adding a custom header with a value from Secrets Manager. One area to pay attention to is the selection of the CloudFront event used to trigger your Lambda function. Some events can be used to trigger the function on every request while others may only execute the function when CloudFront forwards a request to the origin, i.e. when the requested object is not in the CloudFront cache.