Custom name-value pairs associated with this Subscription.
Custom Data is stored in CashBox as a pair of matched text strings, called name-value pairs. You can assign custom data to Billing Plans, Rate Plans, Products, Season Sets, Subscriptions and Customers, each of which is associated with its own Custom Data list. For each of these Objects, CashBox stores a list of Names, which you associate with text string Values. You can use name-value pairs to help you categorize and sort aspects of your system.