Stores data as cookie in the client's browser
Implements a 2-step storage handling a primary storage which needs a visitor ID (e.g. external DB) and a fallback storage which is able to save data without a visitor ID (e.g. session or cookie).


This defines the interface for a persistent targeting storage (e.g. Session). The targeting storage needs to define by itself if it needs a unique visitor ID to store data and fetch if from the visitor info itself.