add blog post title validation config

backend/src/types/Config.ts

@@ -42,6 +42,7 @@ export interface AppConfig {
     signedCookie: SignedCookieConfig;
     validation: {
         productTitleMaxLength: number;
+        blogPostTitleMaxLength: number;
         categoryNameMaxLength: number;
         discountCodeMaxLength: number;
         variantImagesMax: number;