Update user_created field to use username instead

of first_name

src/frontend/src/pages/StorePage/components/market-card.tsx

@@ -172,7 +172,7 @@ export const MarketCardComponent = ({
             </CardTitle>
           </div>
           <span className="text-xs text-primary">
-            by <b>{data.user_created.first_name}</b>
+            by <b>{data.user_created.username}</b>
           </span>
           <CardDescription className="pb-2 pt-2">
             <div className="truncate-doubleline">{data.description}</div>

src/frontend/src/types/store/index.ts

@@ -8,7 +8,7 @@ export type storeComponent = {
   description: string;
   liked_by_count: number;
   liked_by_user?: boolean;
-  user_created: { first_name: string };
+  user_created: { username: string };
 };
 
 export type StoreComponentResponse = {