OldStateAndContract.kt

data class OldState(val a: AbstractParty, val b: AbstractParty) : ContractState {
    override val participants get() = listOf(a, b)
}

open class OldContract : Contract {
    companion object {
        val id = "com.upgrade.OldContract"
    }

    override fun verify(tx: LedgerTransaction) {}

    class Action : TypeOnlyCommandData()
}