fix: fire RecordSaved for tags the post API creates by name

journal-tag is a content type, but tags created on the fly from names in a
post write fired no event, so SEO and sitemap subscribers only heard of them
from a later bulk job. Each created tag now fires a RecordSaved with Created
inside the post write's transaction.

controllers/api/record_events.go

@@ -122,6 +122,22 @@ func postSavedEvent(ctx context.Context, db *gorm.DB, before *postSnapshot, post
 	}
 }
 
+// tagSavedEvent is the RecordSaved of a tag a post write created by name
+// (journal-tag is a content type, D-102): Created, with its name and slug.
+func tagSavedEvent(ctx context.Context, tag *models.Tag) pact.RecordSaved {
+	locale, _ := towel.Locale(ctx)
+	return pact.RecordSaved{
+		Model:   tag.MorphName(),
+		ID:      strconv.FormatUint(uint64(tag.ID), 10),
+		Locale:  locale,
+		Created: true,
+		Changes: []pact.RecordChange{
+			{Attribute: "name", New: tag.Name},
+			{Attribute: "slug", New: tag.Slug},
+		},
+	}
+}
+
 // submittedTranslations lists, per locale, the translated fields a request
 // body submits with a value, in translatedEventFields order. content_html is
 // listed whenever a non-blank content is, as the write derives it from the