Per Jamie's comment in OSSM-3286

At a minimum I think there should be the following in the 2.4 release notes:

A note "Integration with external authorization systems via Authorization policy’s CUSTOM action is a tech preview feature" is now GA (There was a comment in Service Mesh 2.1 that it was Technology Preview...), with a small example config for envoyExtAuthzHttp to show to configure an external authorization.

A similar note for the Prometheus extensions provider with a small sample config, describing how it can be used (I'll defer to Jacek Ewertowski on that). (Confirm if this is TP for 2.4)