Add support for ETag in Dispatcher

[#1]

Request for Feature Enhancement (RFE) Summary:	Since the Dispatcher doesn't support ETags it creates unnecessary traffic between the Dispatcher and the CDN by sending unchanged content.
Use-case:	The page is cached on both CDN and Dispatcher. CDN sends a request to the Dispatcher with the f-None-Match header. The Dispatcher responds with HTTP 200 and the content in the body, even though the content hasn't changed and the CDN already has the latest version.
Current/Experienced Behavior:	The Dispatcher is always returning HTTP 200 code when delivering cached content. Even when the cache ETag header value matches the value of the If-None-Match header in the request.
Improved/Expected Behavior:	The expected behavior would be for the Dispatcher to return HTTP 304 code with no body when ETag matches the value of the If-None-Match header.
Environment Details (AEM version/service pack, any other specifics if applicable):	Latest AEMaaCS - 2024.10.18311.20241017T104455Z
Customer-name/Organization name:	Assa Abloy
Screenshot (if applicable):
Code package (if applicable):

[#2]

@daniel-strmecki 

Thanks for proposing this idea.

This has been reported to the engineering under the internal reference SITES-27072. The product team will triage this request to verify feasibility based on the prioritization model. This post will be updated according to Jira's status.