restore the defaults entry in the network file

[cleverca22]

No description provided.

[cafkafk]

Thanks for your contribution! Could you elaborate a bit on what the motivation behind this PR is, and what it aims to accomplish? It makes it much easier to review :)

[cleverca22]

nixops had a feature where you could specify a defaults entry in the network file, basically:

{
  defaults = {
    documentation.enable = false;
  };
  host1 = ...;
  host2 = ...;
}

and then nixos would merge defaults into every host

morph still has a blacklist to exclude defaults as a valid hostname, but doesnt actually merge it into each host, so it just silently discards this

the PR restores the functionality, so defaults works again

[cafkafk]

This looks good to me 👍

(ping @srhb for second opinion before merge)

[srhb]

agreed!