Blog: allow for "this post has been removed"

Is your feature request related to a problem? Please describe. To make sure we cover our bases, we can have a "this post has been removed" flag that renders a post differently

Describe the solution you'd like We can have a simple flag with a removal notice, with a removal date and some boilerplate text. Text isn't set yet, and may need to be variable (but not lengthy). Said rendering doesn't have an author line or copyright line, or anything like that, just a notice.

We should be able to preserve for our benefit the original article copy, so if needed we can un-remove it by editing that flag. (Maybe we delete it from the file anyway, but that's something we can decide on case-by-case rather than have required by the tech)

Describe alternatives you've considered Just deleting and letting a URL 404, or editing the article's contents manually (and making sure the license line and author area else stays blank)

Additional context None