@bobvanderlinden, thanks for your PR! By analyzing the history of the files in this pull request, we identified @globin, @domenkozar and @fadenb to be potential reviewers.

Why not using serverAliases?

I can imagine it being modeled like this:

          services.nginx = {
            enable = true;
            virtualHosts = {
              "example_http" = {
                serverAliases = [ "example.org" ];
                root = ./wwwroot;
              };
              "example_https" = {
                serverAliases = [ "example.org" ];
                enableSSL = true;
                enableACME = true;
                root = ./wwwroot;
              };
            };
          };

But in that case wouldn't it also be available on the domain-names example_http and example_https? The nginx configuration will have server_name example_https example.org;. I can also imagine ACME not handling this correctly, since it would try to retrieve a certificate for example_https. I haven't tried this yet. I'll give that a shot.

EDIT:
In the above example, when ACME runs, I get the following error:

ACME server returned an error: urn:acme:error:malformed :: The request message was malformed :: Invalid character in DNS name

I think that is because of the _ in the name, choosing a name without _ causes the following error:

Failed to establish a new connection: [Errno -2] Name or service not known

Which makes sense, but it seems the serverAlias is not being used.

I did notice that this PR doesn't handle ACME correctly yet.

I've updated the PR to correctly handle ACME.