Two improvements:

1. Take a username directly instead of a user ID, so I don't have to look up the user ID. I am doing this via authoritative keyserver SQL query for now since it's easy. When we stop relying on the authoritative keyserver I'll need to update it to query the identity service, but this is just a script so it's not very important to get it perfect.
2. Take the parameter as input via CLI, so I don't need to generate a new Docker image every time I want to delete a user (this takes a while).

1. I deployed this change to my personal keyserver
2. I created a dummy test account in production
3. I tested that the script successfully deleted the dummy test account in production