sales/v1 package

SolvencyJSON is the realm's books in one currency: the balance it holds and what it owes, in total and by liability. fees is what SweepFees would pay now. Every movement of quote ends with balance >= owed, so a watcher that sees otherwise has found a fault; what the balance holds above owed was sent outside the entry points and is owed to no one. An empty key or one over 200 bytes panics "invalid currency"; a key that is neither ugnot nor a registered GRC20 aborts in the registry ("unknown token").