Judge the grants step on the declaration it sends, so nothing composed between the check and the send slips through (review of #230)

The guard composed its own declaration ahead of the send; now sendToEach
judges the one it composed and stamped, and refuses it unsent.

cmd/mesh-controller/grants_step_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"errors"
+	"fmt"
 	"slices"
 	"strings"
 	"testing"
@@ -32,9 +33,8 @@ type aSend struct {
 func sendsRecorded(t *testing.T, holder string, behind bool, refuse error) *[]aSend {
 	t.Helper()
 	var sends []aSend
-	wasSend, wasBehind, wasOnly := sendRollout, brokerBehindOf, grantsOnlyOf
-	t.Cleanup(func() { sendRollout, brokerBehindOf, grantsOnlyOf = wasSend, wasBehind, wasOnly })
-	grantsOnlyOf = func(context.Context, *stores, string) (string, error) { return "", nil }
+	wasSend, wasBehind := sendRollout, brokerBehindOf
+	t.Cleanup(func() { sendRollout, brokerBehindOf = wasSend, wasBehind })
 	brokerBehindOf = func(_ context.Context, _ *stores, names []string) (string, bool, error) {
 		if slices.Contains(names, holder) {
 			return holder, false, nil
@@ -123,18 +123,17 @@ func TestAGrantsStepThatFailsIsSaidAndTheSendGoesOn(t *testing.T) {
 	}
 }
 
-// A step whose send would change more than the user list is not sent: it fails, said, and the walk goes on.
+// A step whose send would change more than the user list is refused unsent by the send (sendToEach): the
+// gate says it FAILED with what differed, and the walk goes on.
 func TestAGrantsStepThatWouldCarryMoreIsNotSent(t *testing.T) {
-	sends := sendsRecorded(t, "novox", true, nil)
-	grantsOnlyOf = func(context.Context, *stores, string) (string, error) {
-		return "its send would change more than the bus's user list: -postgres.login-n8n", nil
-	}
+	refusal := fmt.Errorf("%w: its send would change more than the bus's user list: -postgres.login-n8n", errNotGrantsOnly)
+	sends := sendsRecorded(t, "novox", true, refusal)
 	sent, grants, err := sendJudged(t.Context(), nil, "ace")
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(*sends) != 1 || (*sends)[0].keepsAll || strings.Join(sent, ",") != "ace" {
-		t.Errorf("the walk made %+v, want ace's judged send alone", *sends)
+	if strings.Join(sent, ",") != "ace" || len(*sends) != 2 {
+		t.Errorf("the walk made %+v, want the refused step and then ace's judged send", *sends)
 	}
 	if grants == nil || grants.At != nil || !strings.Contains(grants.Failed, "-postgres.login-n8n") {
 		t.Fatalf("the gate keeps %+v", grants)