refactor(actions): enhance error handling and ensure serializability in product actions

frontend/app/kvitto/actions.ts

@@ -5,6 +5,7 @@ import { getAuthHeaders } from '../../lib/auth-headers';
 const API_BASE = process.env.NEXT_PUBLIC_API_URL_INTERNAL || 'http://recipe-api:8080';
 
 export async function createProductAction(name: string) {
+  try {
     const authHeaders = await getAuthHeaders();
     console.log('[createProductAction] Creating product with name:', name);
     console.log('[createProductAction] Auth headers:', authHeaders ? 'YES' : 'NO');
@@ -21,15 +22,25 @@ export async function createProductAction(name: string) {
     }
 
     const product = await res.json();
-  // Return only serializable fields (Dates can't be serialized across RSC boundary)
-  return {
+    console.log('[createProductAction] Response:', product);
+    
+    // Explicitly convert to plain object to ensure serializability
+    const result = JSON.parse(JSON.stringify({
       id: product.id,
       name: product.name,
-    canonicalName: product.canonicalName,
-  };
+      canonicalName: product.canonicalName ?? null,
+    }));
+    
+    console.log('[createProductAction] Returning:', result);
+    return result;
+  } catch (err) {
+    console.error('[createProductAction] Error:', err);
+    throw err;
+  }
 }
 
 export async function updateProductCategoryAction(productId: number, categoryId: number) {
+  try {
     const authHeaders = await getAuthHeaders();
 
     const res = await fetch(`${API_BASE}/api/products/${productId}`, {
@@ -44,11 +55,18 @@ export async function updateProductCategoryAction(productId: number, categoryId:
     }
 
     const product = await res.json();
-  // Return only serializable fields
-  return {
+    
+    // Explicitly convert to plain object to ensure serializability
+    const result = JSON.parse(JSON.stringify({
       id: product.id,
       name: product.name,
-    canonicalName: product.canonicalName,
-    categoryId: product.categoryId,
-  };
+      canonicalName: product.canonicalName ?? null,
+      categoryId: product.categoryId ?? null,
+    }));
+    
+    return result;
+  } catch (err) {
+    console.error('[updateProductCategoryAction] Error:', err);
+    throw err;
+  }
 }