The MessageAttachment struct doesn't have a public initializer

```
public struct MessageAttachment: Codable {
    let fileID: String
    let tools: [AssistantObject.Tool]
    
    enum CodingKeys: String, CodingKey {
        case fileID = "file_id"
        case tools
    }

    public init(fileID: String, tools: [AssistantObject.Tool]) {
        self.fileID = fileID
        self.tools = tools
    }
}
```