serde 1.0.108 on Rust Cargo

Provide a Serializer impl that can write primitives and unit variants to a &mut fmt::Formatter (#1705, thanks @jethrogb)

use serde::Serialize;
use std::fmt::{self, Display};

#[derive(Serialize)]
#[serde(rename_all = "kebab-case")]
pub enum MessageType {
    StartRequest,
    EndRequest,
}

impl Display for MessageType {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.serialize(f)
    }
}