use serde::{Serialize};

#[serde(untagged)]
#[derive(Serialize)]
enum MediaError {
    MissingMediaKey { id: String },
}

fn main() {
    let err = MediaError::MissingMediaKey { id: "some-id".to_string() };
    let json = serde_json::to_value(err).unwrap();
    let child_json = json.as_object().unwrap().values().next().unwrap();

    println!("json: {}", json);
    println!("child_json: {}", child_json);

}