[work in progress] Add products frontmatter, update applies_to as needed

[colleenmcginnis]

Related to elastic/docs-builder#1200

Adds new products frontmatter, which will be used to generate metadata during the build process that the web team will use in the search experience (so users can filter by product). It also checks applies_to and adds additional items based on the products that are covered on the page.

Here's the process:

• Map AsciiDoc/v3 products: @KOTungseth created a list of all AsciiDoc books mapped to:
  • Product names (including the format of the name)
  • applies_to badges associated with the products covered in that book
• Add frontmatter: Then I wrote a script that uses Kaarina's list to look at each Markdown file and:
  • Assign products associated with the AsciiDoc book(s) included in mapped_pages.
  • Check the existing list of applies_to badges for that page and compare it to the list of all applies_to badges mapped to the AsciiDoc book(s) included in that page's mapped_pages.
    • If there are missing applies_to badges, it adds them.
    • If there are additional existing applies_to badges that aren't associated with the mapped_pages, it preserves them (no existing badges should be deleted).
• Format frontmatter: I standardized the order and format of the frontmatter items.
• Validate frontmatter: I created frontmatter.config.yml and checked against it to make sure all frontmatter keys and product values are valid. (Note: I haven't checked that all the values of deployment and serverless options are valid/correctly formatted.)

cc @KOTungseth @reakaleek

[Mpdreamz]

Drive by notes:

• Can we ensure docs-builder validates this?
• Use kebab-case for all products names e.g ECS Logging .NET => ecs-logging-dotnet

[colleenmcginnis]

Can we ensure docs-builder validates this?

Yes! elastic/docs-builder#1200 (comment)

Use kebab-case for all products names e.g ECS Logging .NET => ecs-logging-dotnet

Sure. Would we transform the kebab case version to the formatted text version in docs-builder when adding the meta tag to the HTML? Or should we ask the web team to transform it in the search experience?