Comment 7 for bug 1841932

I'm capturing my thoughts here since we discussed it over IRC.

Tl;dr: the issue is not about the filter itself, this is more the fact that the filter requires you to explicitely create aggregates having the metadata keys matching with the extraspecs you gonna provide.

If you don't want to have such dependency, you need to make this extra spec prefixed by a namespace in https://review.opendev.org/#/c/555861/10/nova/virt/libvirt/driver.py so you'd skip this filter.