Rudder

Until, we weren't specifying magnolia version.
It was not a problem, because only zio-json was using it.
Now, we added difflicious on a plugin, and since we don't explicitly specify magnolia version in core, the plugin uses the version from difflicious (because maven is stupid and doesn't enforce transitive dependency versions), and so we have inconsistencies in macro version and runtime errors.

So, we need to at least track magnolia version.
We should also add difflicious as a tracked test dependency in rudder core, since it looks like something we will need more an more.