画像の有害判定APIの実装

#6 の実装。

```
POST /v1/check
POST Data url=http://path.to/image
```

```
{
  "image": {
    "id": 1,
    "url": "https://oath.to/image",
    "file_name": "file name",
    "local_path": "/path/to/local/image/file",
    "adult_flag": false,
    "grotesque_flag": false
  }
}
```