We need a Rake task that will iterate through all existing logged in kudos and fill in the empty user ID column. Note:
The task should not touch guest kudos (have IPs but no pseud IDs).
The task should not touch orphaned kudos (from deleted accounts: no pseud IDs, no IPs). We don't know what user ID to use anyway.
The task should account for pseud IDs that no longer exist. We don't have foreign key constraints here so this is possible. Don't bother scrubbing the leftover pseud ID, as we'll remove that column in the end.
The task should process kudos in batches and sensibly print its progress... it's a pretty big table.
How to test: this will be mostly on Rake specs. Admins should run this on staging (but after gets to staging). Check that the number of kudos without user IDs go down, and that the remaining ones are indeed either guest or orphaned.
On beta, similarly this task should be run after is also deployed.