feat: slug on the post author object, for author links that do not expose the login

controllers/api/posts.go

@@ -620,7 +620,7 @@ func serializePost(p *models.Post, db *gorm.DB) map[string]any {
 		"is_pinned":          p.IsPinned,
 		"metadata":           jsonField(p.Metadata),
 		"sources":            jsonField(p.Sources),
-		"author":             serializeAuthor(p.User),
+		"author":             serializeAuthor(db, p.User),
 		"categories":         cats,
 		"tags":               tags,
 		"featured_images":    featured,
@@ -683,15 +683,27 @@ func firstImageURL(featured []map[string]any) any {
 	return featured[0]["url"]
 }
 
-func serializeAuthor(user *cabana.BackendUser) any {
+// serializeAuthor is a post's author object. slug is the author's canonical
+// identifier, as on GET /authors/{author}: the author slug when set, otherwise
+// the login, so a consumer links to the author page by slug.
+func serializeAuthor(db *gorm.DB, user *cabana.BackendUser) any {
 	if user == nil {
 		return nil
 	}
+	slug := user.Login
+	if db != nil {
+		var authorSlug string
+		if err := db.Table("backend_users").Select("COALESCE(golem15_bloghub_author_slug, '')").
+			Where("id = ?", user.ID).Scan(&authorSlug).Error; err == nil && authorSlug != "" {
+			slug = authorSlug
+		}
+	}
 	return map[string]any{
 		"id":         user.ID,
 		"first_name": user.FirstName,
 		"last_name":  user.LastName,
 		"login":      user.Login,
+		"slug":       slug,
 	}
 }