Support Ed25519 identities in controller interface

Once legacy/trac#12498 (moved) is merged, we'll be able to identify nodes by ed25519 keys. We should allow the controller to do this too.

This might be a use case for USEFEATURE -- USEFEATURE ed25519-ids could allow us to describe nodes by their best keys, and we could accept ed25519 keys regardless.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information