Update instructions in the contributor guide for generating index page intro/synopsis/abstract as needed. DONE in PR #31127 and  PR #31357.

Fix the diataxis source doc files that use the older :summary: method.

Ensure that all security topics we are bringing downstream use the blurb implementation as per the diataxis template and how-to instructions:

https://quarkus.io/version/main/guides/doc-contribute-docs-howto