fix: fix mock request for funding decorators

src/card/dtos/requests/fund-iban.request.dto.ts

@@ -1,7 +1,9 @@
 import { ApiProperty } from '@nestjs/swagger';
+import { IsString } from 'class-validator';
 import { TransferToJuniorRequestDto } from '~/junior/dtos/request';
 
 export class FundIbanRequestDto extends TransferToJuniorRequestDto {
   @ApiProperty({ example: 'DE89370400440532013000' })
+  @IsString()
   iban!: string;
 }