[TechDocs] optional techdocs-ref annotation.

Right now, you need to define a techdocs-ref annotation pointed to where your documentation lives in your something-info.yaml file (example) to get documentation generated and available in TechDocs.

To avoid this step of configuration, one should be able to use the annotation to connect for example a standalone docs project to your entity but if you have docs with code in the same project, you should not have to define the techdocs-ref.

[freben]

I think it’s worthwhile to always show a docs tab on the entity at least, unconditionally. When the user visits the tab, we can inspect whether there actually seems to exist docs for the entity (through any means necessary - looking for an annotation, and if none exists, go looking in some default place, etc). If they don’t, show an empty state that helpfully explains how to get going.

[kuangp]

I have a use-case that might relate to this issue.

We have a standalone docs project that we’ve registered as a separate entity. We also have multiple components that is associated with the standalone documentation. We would like to be able to connect those components to the same standalone doc entity so that their ‘Docs’ tab will display the same documentation.

Currently adding the annotation pointed to the same doc source repo creates a separate identical doc entry for each component in the techdocs catalog. An alternative could be to split up the documentation itself for each component but that is less desirable since the content is very closely related semantically.