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/posts_helpers.go

@@ -695,54 +695,59 @@ func asUintSlice(raw any) ([]uint, bool) {
 	}
 }
 
-func applyPostAssocs(ctx context.Context, db *gorm.DB, post *models.Post, body map[string]any) error {
+// applyPostAssocs writes the post's categories, tags and translations the
+// body submits. created are the tags the write created by name, for their
+// record events.
+func applyPostAssocs(ctx context.Context, db *gorm.DB, post *models.Post, body map[string]any) (created []models.Tag, err error) {
 	if _, has := body["categories"]; has {
 		ids, _ := asUintSlice(body["categories"])
 		if err := db.Where("post_id = ?", post.ID).Delete(&models.PostCategory{}).Error; err != nil {
-			return err
+			return nil, err
 		}
 		for _, id := range ids {
 			if err := db.Create(&models.PostCategory{PostID: post.ID, CategoryID: id}).Error; err != nil {
-				return err
+				return nil, err
 			}
 		}
 	}
 	if _, has := body["tags"]; has {
-		ids, err := resolveTagIDs(db, body["tags"])
+		var ids []uint
+		ids, created, err = resolveTagIDs(db, body["tags"])
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if err := db.Where("post_id = ?", post.ID).Delete(&models.PostTag{}).Error; err != nil {
-			return err
+			return nil, err
 		}
 		for _, id := range ids {
 			if err := db.Create(&models.PostTag{PostID: post.ID, TagID: id}).Error; err != nil {
-				return err
+				return nil, err
 			}
 		}
 	}
 	if raw, has := body["translations"]; has {
 		if err := syncTranslations(ctx, db, post, raw); err != nil {
-			return err
+			return nil, err
 		}
 	}
-	return nil
+	return created, nil
 }
 
-func resolveTagIDs(db *gorm.DB, raw any) ([]uint, error) {
+// resolveTagIDs turns the submitted tags (ids or names) into tag ids; a name
+// no tag has yet creates the tag, returned in created.
+func resolveTagIDs(db *gorm.DB, raw any) (ids []uint, created []models.Tag, err error) {
 	items, ok := raw.([]any)
 	if !ok {
 		if raw == nil {
-			return nil, nil
+			return nil, nil, nil
 		}
-		return nil, fmt.Errorf("tags must be an array")
+		return nil, nil, fmt.Errorf("tags must be an array")
 	}
-	var ids []uint
 	for _, item := range items {
 		if id, ok := asUint(item); ok {
 			var n int64
 			if err := db.Model(&models.Tag{}).Where("id = ?", id).Count(&n).Error; err != nil {
-				return nil, err
+				return nil, nil, err
 			}
 			if n > 0 {
 				ids = append(ids, id)
@@ -765,11 +770,12 @@ func resolveTagIDs(db *gorm.DB, raw any) ([]uint, error) {
 		}
 		tag = models.Tag{Name: name, Slug: slug}
 		if err := db.Create(&tag).Error; err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		ids = append(ids, tag.ID)
+		created = append(created, tag)
 	}
-	return ids, nil
+	return ids, created, nil
 }
 
 func syncTranslations(ctx context.Context, db *gorm.DB, post *models.Post, raw any) error {