fix promocode creation error display

src/api/promocode/requests.ts

@@ -2,6 +2,7 @@ import { makeRequest } from "@frontend/kitui";
 import { CreatePromocodeBody, GetPromocodeListBody, Promocode, PromocodeList } from "@root/model/promocodes";
 
 import { parseAxiosError } from "@root/utils/parse-error";
+import { isAxiosError } from "axios";
 
 const baseUrl = process.env.REACT_APP_DOMAIN + "/codeword/promocode";
 
@@ -38,6 +39,10 @@ const createPromocode = async (body: CreatePromocodeBody) => {
 
         return createPromocodeResponse;
     } catch (nativeError) {
+        if (isAxiosError(nativeError) && nativeError.response?.data.error === "Duplicate Codeword") {
+            throw new Error(`Промокод уже существует`);
+        }
+        
         const [error] = parseAxiosError(nativeError);
         throw new Error(`Ошибка создания промокода. ${error}`);
     }