End user applications built with this library have per TLD DoH resolvers (example).

Including the URL of DoH endpoint helps end user to self-service when one of DoH resolvers goes down (example: ipfs/boxo#772)

Demo

Let's assume https://example.com/dns-query responsible for resolving .test TLD is down.

Without this PR, user gets confusing error:

$ curl http://this-fails.test.ipns.localhost:8088/
failed to resolve /ipns/this-fails.test/: DNSLink lookup for "this-fails.test." failed: HTTP error: "405 Method Not Allowed" [405

With this PR, end user gets meaningful error HTTP error: "405 Method Not Allowed" [405] from "https://example.com/dns-query"

$ curl http://test.crypto.ipns.localhost:8090/
failed to resolve /ipns/this-fails.test/: DNSLink lookup for "this-fails.test." failed: HTTP error: "405 Method Not Allowed" [405] from "https://example.com/dns-query"