support prefilling for arbitrary zone
Ulrich from IIS requested feature which would allow them to prefill resolver's cache with arbitrary zone, i.e. not only root zone.
Technical note:
Simple removal of checks for zone name does not work because DS
records are missing in cache and this lead to failing validation. Maybe we can just wrap import in a function which requests DS
and calls import from query callback?
Edited by Petr Špaček