The accounts directory is based on the hash of the settings.
https://github.com/NixOS/nixpkgs/pull/270221 changed the default of
security.acme.defaults.server from null to the default letsencrypt URL
however as an unwanted side effect this means the accounts directory
changes and the ACME module will create a new a new account.
This can cause issues with people using CAA records that pin the
account ID or people who have datacenter-scale NixOS deployments
We allow setting this option to null again for people who want
to keep the old account and migrate at their own leisure.
Fixes https://github.com/NixOS/nixpkgs/issues/316608
Co-authored-by: Arian van Putten <arian.vanputten@gmail.com>
d1f07e6382