The goal of T348388: Use central login wiki for login (SUL3) is to end up with a login/signup flow that provides unfettered access (as much as possible) to cookies on the central login domain. The more straightforward part of that is ensuring that users interact with the central domain (which is done my moving the login form over there), but there are a number of choices beyond that will influence cookie access limits on various browsers. This task is about pinning down the details of the login and signup flows that are relevant in terms of browsers' third-party cookie blocking policies.