@NonNull abstract fun setContactKey(@NonNull contactKey: String): Editor
Setter for contactKey which was formerly known in the SDK as SubscriberKey. The name was changed to align the SDK's nomenclature with the Marketing Cloud Contacts DB.
A ContactKey, once set, may never be unset. If a ContactKey is not provided the Marketing Cloud will generate a random GUID to serve as a ContactKey until one is set by the SDK.
contactKey - String: any non-null string with at least 1 non-white space character.
Return
Editor: RegistrationManager.Editor