Configuration test xml

follow-up for #103 - there are some issues with xml that i hope somebody can help me with.

until #103 is merged, this will also show all changes of #103
this is not how it should look like to match the configuration, which is a scalar node:

```xml
<headers last-modified="-1 hour" reverse-proxy-ttl="42">
    <cache-control name="public">true</cache-control>
    <cache-control name="max-age">300</cache-control>
</headers>
```