Remove yojson dependency, require mirage-crypto >= 2.0.2
- Remove all yojson dependencies from dune-project (fully migrated to atproto-json)
- Add atproto-json dependency to packages that need JSON (lexicon, identity, api)
- mirage-crypto-ec and mirage-crypto-rng already require >= 2.0.2
Note: mirage-crypto-rng-eio 1.2.0 pins all mirage-crypto packages to 1.2.0
which has a P-256 signature verification bug. Do not install it.