Get customer selections

Resolve which customer a customer page opens. Pass a customer's id, customer key, or the id of the run that generated it to select that customer, or "default" for the newest active customer of businessProfileId (a profile id or profile key), else its newest archived one, else the organization's newest active customer, else its newest archived one; an id that names no customer also yields that default. Returns the selected customer's id, customer key, and business profile (null when the organization has no customer), and every business profile that has customers, to switch between.