added createdAt info in user data and added types of elements to render in the list in order to have a more coherent look and a simpler api for the ElementList user

front/models/UserData.ts

@@ -2,6 +2,7 @@ interface UserData {
     partyPlayed: number;
     xp: number;
     avatar: string | undefined;
+    createdAt: string;
 }
 
 export default UserData;