Accound needs business status (ready for billing|billed|paid...)

Account resource has status element (active | inactive | entered-in-error | on-hold | unknown) but also needs an element to represent the status of the account within a business process while active (possible values e.g. "ready for billing", "billed", "balanced/paid" etc.)

Suggest to add element "billingStatus" as CodableConcept to the Account Resource