An outbound calling campaign, identified by its :code.
Fetch one with Guava.Campaigns.get_by_code/2 or Guava.Campaigns.list/1.
The :id field is internal
Campaigns also carry a legacy id, which a few API endpoints are still keyed
on. It's kept here so those endpoints can be called without an
extra lookup, but it is not part of the public API — no Guava.Campaigns
function accepts one, and it will disappear once those endpoints move to v2.
Identify campaigns by :code.