While reviewing elastic/apm-agent-dotnet#2650, I realized how little information we have in the docs-builder docs about how to use products metadata.

In addition to the list on the frontmatter docs page, we should also add:

• Documentation on using products in docset.yml to apply metadata to every page in a doc set.
• Guidelines on how to choose which products to include. Some factors to consider:
  • Think about how users will use this data via search¹ (for example, if a user was searching for information on Elastic Cloud Serverless and filters to pages that are tagged with cloud-serverless, does it make sense to include a page from the APM .NET agent docs?).
  • Avoid just duplicating information in applies_to (for example, just because a page describes functionality that is applicable to a specific deployment method doesn't mean the page is about that deployment method).
• Anything else?

cc @theletterf