Feature Request: Add “NXDOMAIN Consensus” Load-Balancing Strategy

Hello,

First, thank you for maintaining dnscrypt-proxy — it’s an excellent project that I use daily.

I’d like to propose a new load-balancing strategy for situations where strict consensus is required across multiple upstream resolvers. Specifically:

Current strategies (e.g. p2) return the fastest valid response.

Proposed strategy (consensus):

• Query all configured upstream resolvers in parallel.
• If any resolver returns NXDOMAIN, dnscrypt-proxy should return NXDOMAIN.
• Otherwise, return the first valid answer as usual.

This would be useful for scenarios where a single NXDOMAIN should be treated as authoritative, even if other resolvers provide a response.

Would you consider adding such a strategy (e.g., lb_strategy = consensus) to dnscrypt-proxy?

Thank you for your time and for all the work that goes into this project.