Name a deleted target on its historical deliveries (closes #211)

Deleting a target soft deletes its row while its deliveries survive
in the per-webhook database, so the event log kept rendering the
history and lost the label: every historical row read ": delivered"
and the deliveries block was headed by an empty name.

loadTargetMap already loaded soft-deleted rows Unscoped for the
redactor half, then discarded them before building the view half.
It now builds both halves from every loaded row, and TargetView
carries a Deleted flag with a DisplayName that renders
"name (deleted)" — an operator debugging an old delivery needs to
know the target is gone, not just what it was called.

The views still come from NewTargetViews, so a deleted target's
configuration is masked by exactly the code that masks a live
one's. The widening is confined to this map, which feeds only
DeliveryView.Target on the event log page: the source detail
target list, the target edit form, the receiver and resubmit fan-out
and the delivery engine each resolve targets through their own
scoped queries, and the replay path keeps refusing a deleted target.

internal/delivery/target_config_view_test.go

@@ -2,9 +2,11 @@ package delivery_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
 )
@@ -17,6 +19,14 @@ const (
 	slackWebhookURL = "https://hooks.slack.com" +
 		slackSecretPath
 
+	// slackMaskedURL is what a Slack webhook URL renders as
+	// once masked: scheme and host, path elided.
+	slackMaskedURL = "https://hooks.slack.com/..."
+
+	// slackTargetName is the target name the Slack projection
+	// tests use.
+	slackTargetName = "slack-target"
+
 	viewExampleOrigin = "https://example.com"
 	viewExampleHook   = viewExampleOrigin + "/hook"
 	viewMaskedOrigin  = viewExampleOrigin + "/..."
@@ -33,7 +43,7 @@ func TestMaskedWebhookURL(t *testing.T) {
 	}{
 		"slack webhook": {
 			url:  slackWebhookURL,
-			want: "https://hooks.slack.com/...",
+			want: slackMaskedURL,
 		},
 		"query string dropped": {
 			url:  viewExampleOrigin + "/a?token=secret",
@@ -125,23 +135,61 @@ func viewFor(
 	return views[0]
 }
 
-func TestNewTargetViews_Slack(t *testing.T) {
+// TestNewTargetViews_DeletedTarget proves the projection marks
+// a soft-deleted target's name and masks its configuration by
+// the same rules a live target's is. Delivery history outlives
+// the target it names, so this projection is what an operator
+// reads about a target that no longer exists.
+func TestNewTargetViews_DeletedTarget(t *testing.T) {
 	t.Parallel()
 
-	view := viewFor(t, database.Target{
-		Name:   "slack-target",
+	target := slackTarget()
+	target.DeletedAt = gorm.DeletedAt{
+		Time:  time.Now(),
+		Valid: true,
+	}
+
+	view := viewFor(t, target)
+
+	assert.True(t, view.Deleted)
+	assert.Equal(t, slackTargetName, view.Name)
+	assert.Equal(
+		t, slackTargetName+" (deleted)", view.DisplayName(),
+	)
+	assert.Equal(
+		t,
+		map[string]string{"Webhook URL": slackMaskedURL},
+		fieldMap(view.Config),
+	)
+}
+
+// slackTarget is the live Slack target the projection tests
+// share.
+func slackTarget() database.Target {
+	return database.Target{
+		Name:   slackTargetName,
 		Type:   database.TargetTypeSlack,
 		Active: true,
 		Config: `{"webhookUrl":"` +
 			slackWebhookURL + `"}`,
-	})
+	}
+}
+
+func TestNewTargetViews_Slack(t *testing.T) {
+	t.Parallel()
+
+	view := viewFor(t, slackTarget())
+
+	assert.Equal(t, slackTargetName, view.Name)
+
+	// A live target is never marked, so the marker cannot
+	// reach a name that still exists.
+	assert.False(t, view.Deleted)
+	assert.Equal(t, slackTargetName, view.DisplayName())
 
-	assert.Equal(t, "slack-target", view.Name)
 	assert.Equal(
 		t,
-		map[string]string{
-			"Webhook URL": "https://hooks.slack.com/...",
-		},
+		map[string]string{"Webhook URL": slackMaskedURL},
 		fieldMap(view.Config),
 	)
 }
@@ -212,7 +260,7 @@ func TestNewTargetViews_HTTPMasksDestinationURL(t *testing.T) {
 
 	assert.Equal(
 		t,
-		"https://hooks.slack.com/...",
+		slackMaskedURL,
 		fields["Destination URL"],
 	)