NewCurrencyStates gets a new type for tracking exchange currency states.

ErrCurrencyStateNotFound is an error when the currency state has not been found TODO: distinguish between unsupported and not found.

Currency defines the state of currency operations.

Options defines the current allowable options for a currency, using a bool pointer for optional setting for incomplete data, so we can default to true on nil values.

Snapshot defines a snapshot of the internal asset for exportation.

States defines all currency states for an exchange.