- Transactions: new final status `cancelled`. TransactionInfo::isTerminal()
  returns true for it, and the transaction webhook is sent for it.
- SignTransactionResponse::$supersededUuids: EVM signatures from the same
  address that were not executed and were replaced by this one.
- TransactionInfo::$errorReason: why a transaction is failed, expired or
  cancelled, or why a signed one cannot be executed yet.
- ErrorCode: NonceGap, NonceAlreadyUsed, PreviousExecuteUnresolved.