Yep, I already have server-sided collection, but client-side would be great. Oh well, thanks everybody!
You could alternatively store the IP along in the database and have clients send the ID and Name, fetch the old IP from the database and see it that works when authenticating, if so update the database.
That way it'll work for users who have kept the same IP.
An example of that situation.
User A is hosting a server with Updater, User B joins under the name of "BlocklandX", the IP and Name is sent to the Updater server like normal.
User B then leaves to join a server User C is hosting without Updater.
User D which is in User C's server has Updater, sends the ID and Name of User B under the name of "OtherName" to the Updater server.
The server then sees that it has logged the ID, and fetches the IP tied with it and updates the name if it indeed auths.