fix: IndexNow hears of deleted and edited records

RecordDeleted marks the listed rows it excludes and RecordSaved the rows
whose lastmod it moves (indexnow_pending_at); the next rebuild sends
them to IndexNow as removed or changed and clears the marks. RecordSaved
checks for a nil event before reading it. TestIndexNow now deletes and
edits through the record events, as the admin does.

updates/202611040001_add_golem15_sitemap_urls_indexnow_pending.go

@@ -0,0 +1,27 @@
+package updates
+
+import (
+	"github.com/go-gormigrate/gormigrate/v2"
+	"gorm.io/gorm"
+)
+
+// addIndexNowPending adds indexnow_pending_at to golem15_sitemap_urls
+// (P33-62): the record listeners mark the rows of a deleted record that
+// were listed, and the rows of an edited record whose lastmod moved, so
+// the next rebuild sends them to IndexNow as removed or changed and clears
+// the mark.
+var addIndexNowPending = []*gormigrate.Migration{
+	{
+		ID: "202611040001_add_golem15_sitemap_urls_indexnow_pending",
+		Migrate: func(tx *gorm.DB) error {
+			return tx.Exec(`ALTER TABLE golem15_sitemap_urls ADD COLUMN indexnow_pending_at TIMESTAMPTZ NULL`).Error
+		},
+		Rollback: func(tx *gorm.DB) error {
+			return tx.Exec(`ALTER TABLE golem15_sitemap_urls DROP COLUMN IF EXISTS indexnow_pending_at`).Error
+		},
+	},
+}
+
+func init() {
+	Register(addIndexNowPending...)
+}