I dont like the ```if record_type? :SOA``` at the end of each method.
I'm not sure how we could make this better, but maybe we could try something like:
```
included do
  ...
  send(:include, SOAInstanceMethods) if self.record_type? :SOA
end

module SOAInstanceMethods
  def soa_content_primary
    soa_content[0]
  end
  ...
end
```
but i think we can't access ```self.record_type?``` at this point.
Any idea how to handle this?