Review and define the back-end APIs of the experimental module

Useful for reference: https://www.drupal.org/about/core/policies/core-change-policies/bc-polic... →

Although from that page, note:

Note that in addition to changes allowed here, Drupal 8 and above also includes experimental modules. These modules have their own versioning that does not follow semver (semantic versioning), and any APIs provided by such modules should be considered exempt from this policy.

My read on that is marking our @internal APIs is not necessary for experimental inclusion, but will be necessary long term, as part of full non-experimental adoption into Drupal core.

First iteration of the API definition marking some features as internal/final.

Would be great to have a second pair of eyes on this to ensure that I understood it correctly.

Thank you!

Moving to Needs work after getting Navigation into core.

Closing this issue as outdated. This came before the big change in the admin of Navigation over to layout builder. Most of the changes in the navigation contib MR here don't apply anymore. We can open specific follow up issues on an as needed basis for the current state of the navigation module codebase.