[Add] My single use case

[Martin Thomson <[e-mail]>]

My preference is to tackle just this:

As a new device or application, when I join a network that I have no prior relationship with or configuration for, I want to discover the DoT or DoH resolver that corresponds to the Do53 resolver offered by that network.

This might need the full matrix of DoT/DoH, v4/v6, with/without a forwarder, but this is fundamentally just a single use case.

Specifically, I want to NOT learn about whether the resolver does qname minimization or DoT to the authoritative or whether it does the eDNS client subnet or different policies with respect to what is answered or anything else that might make a decision to use this alternative complicated.  Existing methods don't provide this information.  I don't want a protocol that does anything fancy because that makes the decision complex.