Upgrade to HPKE v0.14

[rozbb]

Making this to start the conversation about how to upgrade. Right now it's the absolute minimum possible diff to do the upgrade. But I suspect you might want to change your own feature flags to match the new ones upstream, and also maybe add some to expose the new PQ and hybrid ciphersuites. Let me know what you're thinking

[tgeoghegan]

Thanks for the PR, Michael.

IMO this crate's goal is just to be an adapter to hpke that allows runtime dispatch. If we introduce any abstractions on top of hpke, like a different set of features, we're doing a disservice to users by getting in the way of what they really want to do. So what I mean by all that is: we should harmonize hpke-dispatch's features with hpke.

We will also need to update the discussion of features in README.md before merging.

And wiring up PQ and hybrid HPKE is worthwhile.

[tgeoghegan]

the hpke/std feature is gone, but AFAICT that's because instead of that gating an std::error::Error impl on HpkeError, that's now a core::error::Error impl that can be available unconditionally.

[rozbb]

Yup

[divergentdave]

We'd still need default-features = false in order for enabling hpke/x25519 etc. again to have any effect.

[rozbb]

Great, I can make those changes 👍

[tgeoghegan]

Thanks, but let's see if @jcjones or @divergentdave have an opinion to share before we make another move.

[divergentdave]

Mirroring hpke's features and forwarding them sounds good. Our existing per-algorithm features may have gone a bit overboard.

[divergentdave]

We'd still need default-features = false in order for enabling hpke/x25519 etc. again to have any effect.