[knot-dns-users] Feature Request: Opportunistic dnssec-signing

Hi, I am trying to make DNSSEC signing orthogonal to zone data transport in the DNSSEC signer solution for SURFnet. This translates directly to an intuitive user interface, where domain owners can toggle DNSSEC on and off with a flick of a switch. Interestingly, keymgr can work orthogonally to zone data; keys can be added and removed, regardless of whether a zone has been setup in Knot DNS. Where the orthogonality is broken, is that I need to explicitly set dnssec-signing: to on or off. This means that I need to create a zone, just to be able to tell Knot DNS about the keys. Of course there are complaints when configuring Knot DNS without a zone data file present. The most elegant approach would be to setup dnssec-signing as opportunistic option, meaning "precisely then when there are keys available in the keymgr for this zone". Such a setting could then end up in the policy for any such zone, and that can be done when the zone data is first sent, without regards of what we try to make an orthogonal dimension. I have no idea if this is difficult to make. I do think it may be a use case that wasn't considered before, which is why I'm posting it here. If this is easy and doable, please let me know; otherwise I will have to work around Knot DNS (ignoring errors, overruling previously set content just to be sure it is set, and so on) to achieve the desired orthogonality. Cheers, -Rick