### Describe the bug create submission에 contestId를 지정해 주고 정상적인 요청 후 get submissions를 통해 생성한 레코드를 확인하였을 때 contestId값이 null로 표시됩니다. ### Reproduction 1. 2. 3. ### Logs _No response_ ### System Info _No response_ ### Validations - [X] Follow our [Code of Conduct](https://github.com/skkuding/next/blob/main/CODE_OF_CONDUCT.md) - [X] Read the [Contributing Guidelines](https://github.com/skkuding/next/blob/main/CONTRIBUTING.md) - [X] Check that there isn't already an issue