Backports the following commits to 7.x: Rename template V2 classes to ComposableTemplate (#57183)
This documents the index template v2 and component template APIs in the high level rest client. (cherry picked from commit 9bcf89b1e27613ab8887ce611ec2b0d1356cba8b) Signed-off-by: Andrei Dan <andrei.dan@elastic.co>