message: [types] Prefer error escalation over unwrap
  With unwrap here, a client can send a bad key or signature and cause
  the AC to crash.
diff: @@ -661,8 +661,8 @@ impl CanonicalDeserialize for SignedTransaction {
  Ok(SignedTransaction::new(
  raw_txn,
  - Ed25519PublicKey::try_from(&public_key_bytes[..]).unwrap(),
  - Ed25519Signature::try_from(&signature_bytes[..]).unwrap(),
  + Ed25519PublicKey::try_from(&public_key_bytes[..])?,
  + Ed25519Signature::try_from(&signature_bytes[..])?,
  ))
  }
  }
  