Blog: allow for "this post has been removed"

[ryanmacklin]

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

[ryanmacklin]

Removal should list date of removal

[ryanmacklin]

Said pages should also not render in postbox pages--blog landing page and author pages

[bwklein]

If we set a post frontmatter field draft: true or just delete the file, the post will not be on our public site anymore.

Is there a reason to keep the post content and have it show up on the site in lists, or it's own page with a notice that it has been removed? (I assume this is to give a landing place, better than a 404 for people coming from a link outside of our site.)

We could also make a single landing page on the site that we can redirect a 'removed' post to. We could then just add that post URL to a list of redirects in the netlify.toml config file for the server.

[bwklein]

@ryanmacklin do you have a preference? ^