Add support for single-sourced license level information

[bmorelli25]

Summary

We currently treat https://www.elastic.co/subscriptions as the source of truth for feature licensing information. We avoid adding licensing information to the documentation as it can be easy to forget to update this information in multiple places when it inevitably changes.

In V3, we should explore the ability to single-source feature licensing information. For example, if we had a single yaml or json file that the product team could add licensing information to, we could potentially show specific license levels in the docs. IMO, this would be a better user experience than forcing folks to go to a different page to determine if the feature they want to use is supported by their current subscription.

[lcawl]

My two cents would be that we'd still want these details to point to the website as the source of truth in the case folks forget to keep them in sync.

It would also be interesting to ponder how this information would be shown on a page. A particular page might cover multiple features, so would that need to be added as metadata or in a prerequisites section? Or are you thinking it would be like hovers that appear any time a specific feature name is used? If so, it gets close to the admonition discussions about when/if it would be useful vs noisy.

[bmorelli25]

I don't know what I'm envisioning yet tbh. But I do think the ideal user experience would be to not have to leave the page to see the subscription level of the feature you're reading about. I'm also thinking that when we eventually allow users to log into the docs, we'd want to be able to call out that the feature they're reading about is or isn't supported by their current subscription level.

There's an opportunity to both provide a better user experience and upsell directly in the docs if we get specific about feature levels.

[bmorelli25]

@dedemorton attempted something similiar in our asciidoc build, but it was not approved by eng leaders. elastic/docs#476.