*ring* versions 0.16.20 and earlier are unmaintained

[briansmith]

Occasionally I get bug reports where people seem to be using ring 0.16.20 or even earlier versions from years ago. I would like to mark them all as "unmaintained" in a way that doesn't disrupt people. I suspect that many people might have been holding onto using 0.16.20 since no bugs have ever (AFAICT) been reported against it and because aws-ls-rs has an API that is compatible with 0.16.20 but not later versions like 0.17.

I don't give any thought to 0.16.20 or earlier versions at all, for several years now, and I've plainly stated so.

I don't know if there is a way to make an "unmaintained" notice for 0.16.20 and earlier but which doesn't bother users of 0.17 and later. Is there?

ring 0.16.20 was released over 4 years ago so presumably this is stating the obvious, but I guess it matters.

[tarcieri]

The unmaintained crate advisories work like any other advisory, so we could remove withdrawn and add >= 0.17 to e.g. unaffected

[briansmith]

If that works, that's great.

[briansmith]

Let's hold off on that until the discussion in briansmith/ring#2450 is further along.

[briansmith]

Resolved in PR #2244. Great work everybody!