Background
One goal of the IP Masking project is that wikis with temporary account autocreation enabled should not store a user's IP address anywhere other than (temporarily) in the CheckUser tables.
Currently IP addresses are stored in the actor table's actor_name column whenever an anonymous actor is created. New actors are created in various places, for example when saving a recent change or making a log entry: https://codesearch.wmcloud.org/deployed/?q=acquireActorId&files=&excludeFiles=&repos=
Eventually temporary accounts will be autocreated for all actions that cause an IP actor to be created. However, there are a lot of existing code paths to be updated, and we should ensure that any new features that attempt to save an IP actor fail in their attempt. We can ensure that IP address names do not pass validation checks for insertion into the actor table.
To do
ActorStore::validateActorForInsertion should fail if the user passed to that method has an IP address for a username.