Allow for passing in additional order fields

[petercooperjr]

This allows for the caller to add notBefore/notAfter for servers that support them, or the "replaces" field which is added in draft-ietf-acme-ari for servers that support ARI. (Again, not sure if there might be a better approach. I'm pretty sure all supported versions of node support the way I used the spread operator, but it may be that one want to copy the fields a different way, or explicitly list which fields one wants to allow the caller to specify.)