Add SRC user recognition use case

privacy/use-cases/src.md

@@ -5,9 +5,10 @@ See more [information about EMV®SRC](https://www.emvco.com/emv-technologies/
 
 ## Overview of Click-to-Pay Flow
 
-* The user pushes the Click-to-Pay button on a merchant site. This is typically provided by another party, the SRC Initiator (SRC-I), in a 3p context.
-* The SRC-I determines (via a cookie, typically) whether this is a returning user, and if so finds the user's SRC identity (e.g., email address).
-* The SRC-I dispatches the identity to different SRC systems (typically the card networks) and aggregates the responses into a candidate card list (i.e., cards registered in SRC systems under that user identity).
+* During an enrollment phase, the user registers a card with an SRC System; thusthe SRC System has a relationship and uses cookies to recognize returning users.
+* At transaction time, the user pushes the Click-to-Pay button on a merchant site. This is typically provided by another party, the SRC Initiator (SRC-I), in a 3p context.
+* The SRC-I interacts with each SRC system (by dispatching SRC system cookies to their servers) to establish whether this is a returning user, and if so, to retrieve registered cards.
+* The SRC-I aggregates the responses into a candidate card list (i.e., cards registered in SRC systems under that user identity).
 * The SRC-I displays the list of cards to the user for selection.
 * (The rest of the flow happens, but it is not essential to understanding the problem statement.)