@Nullable abstract fun getContactKey(): String?
Getter for contactKey, formerly known as SubscriberKey in the SDK. The name has been changed to align the SDK with the Salesforce Marketing Cloud Contacts DB. If ContactKey is unset then a random GUID will be set in the Marketing Cloud.
Note: once this value is set from the SDK it may not be empty or null. There is no way to clear or unset a Contact Key.
Return
String?: null or the set value.