Take the Tor exit list from Onionoo, which has the IPv6 exits (closes #234)

check.torproject.org lists IPv4 exits only, so is_tor was false for an IPv6
exit. tor_exits now comes from Onionoo's details document, read by a new
format that takes every address in exit_addresses and or_addresses.

Model: opus-5-5

internal/iplist/parse.go

@@ -164,6 +164,17 @@ func addDShieldNetwork(builder *netipx.IPSetBuilder, line string) error {
 	return nil
 }
 
+// onionooDetails is the part of an Onionoo details document that holds the
+// relays' addresses.
+//
+//nolint:tagliatelle // Onionoo's own field names
+type onionooDetails struct {
+	Relays []struct {
+		ExitAddresses []string `json:"exit_addresses"`
+		ORAddresses   []string `json:"or_addresses"`
+	} `json:"relays"`
+}
+
 // parseOnionoo returns every address in the exit_addresses and or_addresses
 // fields of the relays in an Onionoo details document. A document with no
 // addresses fails, because the Tor network always has relays.
@@ -173,13 +184,7 @@ func parseOnionoo(r io.Reader) (*netipx.IPSet, error) {
 		return nil, err
 	}
 
-	//nolint:tagliatelle // Onionoo's own field names
-	var details struct {
-		Relays []struct {
-			ExitAddresses []string `json:"exit_addresses"`
-			ORAddresses   []string `json:"or_addresses"`
-		} `json:"relays"`
-	}
+	var details onionooDetails
 
 	err = json.Unmarshal(data, &details)
 	if err != nil {