Slightly change services.nginx.configuration to allow for merging

[MagicRB]

This might break someone's config an is untested, but without it, the following won't work:

[
  {
    services.nginx.configuration = [
      {
        http."" = {
          ...
        };
      }
    ];
  }
  {
    services..nginx.configuration = [
      {
        stream."" = {
          ...
        };
      }
    ];
  }
]

currently that'll fail with

error: The option `services.nginx.configuration' is defined multiple times while it's expected to be unique.

which is less than ideal for composability.

EDIT: this will break everything, 100% and also introduces infrecs in its current form

[MagicRB]

After some friendly back and forth with the nix command line I managed to make it work.

[MagicRB]

This exploration led me to a different issue, Nginx doesn't merge http { ... } blocks, which makes sense, but that means that "mixins" such as:

{lib, ...}: {
  services.nginx.configuration = lib.mkBefore {
    http."" = {
      server."" = {
        listen = ["80" "default_server"];

        location."/" = {
          return = ["301" "https://$$host$$request_uri"];
        };
      };
    };
  };
}

end up in their own HTTP block and cannot set defaults and are unaffected by other mixins, in other words they're useless. Not really sure what's the solution in this case. Composability of Apache and Nginx modules is horrible due to this, only way to compose is to use the runtime include = [] mechanism, which is okay I guess but not great.