🚚(newsletter) rename newsletter subscription token attribute

The attribute that stores the newletter subscription has been renamed in
Joanie.
It has been renamed here too for simplicity.

fonzie/views/user.py

@@ -75,7 +75,7 @@ def get(self, request, version, format=None):
         )
         if "newsletter_subscribed" in request.COOKIES:
             # delete the cookie, as we only need it once, after registration
-            token.payload["has_subscribed_to_newsletter"] = (
+            token.payload["has_subscribed_to_commercial_newsletter"] = (
                 request.COOKIES.get("newsletter_subscribed") == "true"
             )
             response.delete_cookie("newsletter_subscribed")