feat(identity): make Keypair and Publickey opaque

[tcoratger]

Description

Keypair and Publickey are rendered opaque:

• Keypair is replaced by a private KeyPairInner enum that is encapsulated inside the Keypair pub struct
• Publickey is replaced by a private PublickeyInner enum that is encapsulated inside the Publickey pub struct

Resolves #3860.

Notes & open questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

Direction looks good to me, a few minor comments!

Thanks for all your contributions :)

[dariusc93]

Didnt notice the PR. Its a great start here.

Since I am not able to make a comment on the line itself, In x25519.rs on line 129 make sure to change logic in X25519::linked so it is using PublicKey::try_into_ed25519

[thomaseizinger]

Thank you for the additional help in reviewing @dariusc93, much appreciated! :)

[thomaseizinger]

Really good work, looking forward to merging this, thank you!

A few minor comments but direction looks good.

[dariusc93]

Cant comment on the line itself but on line 281 should be changed to KeypairInner::Ecdsa(key.into())

[thomaseizinger]

Awesome, I am excited to land this!

Only a few more minor things :)

[mergify]

This pull request has merge conflicts. Could you please resolve them @tcoratger? 🙏

[thomaseizinger]

Thanks!

This is a very exciting PR to land, it should make everything around Keypair and PublicKey much easier to use.

[tcoratger]

Thanks!

This is a very exciting PR to land, it should make everything around Keypair and PublicKey much easier to use.

@thomaseizinger Thanks for your help, nice library to collaborate :)

[folex]

Hi! I've some API concerns about that change. It makes some of our code pretty hairy.

#3860 (comment)

Hope to discuss that problem and look for possible solutions! Thank you.