Wrong publish menu status for custom content provider

Description

Forum post: https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2019/12/custom-contentproviders-has-not-published-yet-/

A customer is using a custom content provider with this code:

IVersionable.Status = VersionStatus.Published;
IVersionable.IsPendingPublish = false;
IVersionable.StartPublish = DateTime.Now.AddDays(-1);

If you open a file under Media > Provider and click the Publish button, the status shows "Not published yet". One expects it to be "Published," with a link to that file.

The UI determines the message based on the value of the PublishedBy field. This is incorrect. The UI message should be based on content status.