what does this service do?
what do I need to know as a user?

Ansible and Docker Compose.

Deleting users from Zammad can be difficult; we had problems remmoving them through the data privacy cleanup job (see https://zammad.hamburg.ccc.de/#system/data_privacy)

Instead, you can remove users through the command line:

# docker exec zammad-docker-compose-zammad-railsserver-1 /docker-entrypoint.sh rails console
> user = User.find_by(login: "hans.acker@example.com")
=> #<User:0x00007fc29284eed0
 id: 69,
 organization_id: nil,
...
> user.destroy
=> #<User:0x00007fc29284eed0
 id: 69,
 organization_id: nil,
...