Decide how to handle cleaning up defunct groups

[LordOfPolls]

https://github.com/LordOfPolls/Unifi-Rampart/blob/master/src/main.rs#L81-L85

  // there are more than max items in the list, split it into multiple lists, and upsert each of them
  // todo: if a list shrinks later, we should remove it from the database
  // question would then be how to handle for any firewall groups that reference it...
  warn!("IP list '{}' exceeds max items limit of {}, splitting into multiple lists", source.name, cfg.application.max_items_in_list);
  let split_ips = ips.chunks(cfg.application.max_items_in_list - 1);

Need to decide how to handle for this case.

It might be possible to add a column to the ace,FirewallGroups collection without UniFi freaking out; if thats thet case, we can track which groups are being created by this application.
need to test...

That way, the user can use whatever names they like, but we can keep track of which groups we need to maintain.