feat: add durable Kuknos settlement coordination

cmd/dashboard-loadtest/main_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"sync/atomic"
@@ -10,7 +11,7 @@ import (
 )
 
 func TestRunSendsConcurrentRequestsAcrossTargets(t *testing.T) {
-	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, _ *http.Request) {
+	server := newIPv4TestServer(http.HandlerFunc(func(response http.ResponseWriter, _ *http.Request) {
 		response.WriteHeader(http.StatusOK)
 		_, _ = response.Write([]byte("ok"))
 	}))
@@ -49,7 +50,7 @@ func TestPercentileUsesNearestRank(t *testing.T) {
 
 func TestRunDrainsInflightRequestAfterDuration(t *testing.T) {
 	var canceled atomic.Bool
-	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
+	server := newIPv4TestServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
 		time.Sleep(20 * time.Millisecond)
 		if request.Context().Err() != nil {
 			canceled.Store(true)
@@ -66,3 +67,14 @@ func TestRunDrainsInflightRequestAfterDuration(t *testing.T) {
 		t.Fatalf("in-flight request was not drained cleanly: %+v", result)
 	}
 }
+
+func newIPv4TestServer(handler http.Handler) *httptest.Server {
+	listener, err := net.Listen("tcp4", "127.0.0.1:0")
+	if err != nil {
+		panic(err)
+	}
+	server := httptest.NewUnstartedServer(handler)
+	server.Listener = listener
+	server.Start()
+	return server
+}