I ended up not being able to work it out. I took a compromise where strings could be passed through extensions normally, I converted the enum type to a string, and then converted the string to an enum in mapper_response

#[derive(Debug, Deserialize, Clone, AsRefStr, EnumString)]
#[serde(tag = "type", content = "data")]
pub enum Error {
    LoginFail,

    // Auth error
    AuthFaildNoAuthTokenCookie,
    AuthFaildTokenFormatWrong,
    AuthFaildCtxNotInRequestExt,

    // model errors.
    ListenerCreationFailed(ListenerCreationError),
    ListenerRemoveFailed,
    ListenerEditFailed,
}

mapper_response:

response.extensions_mut().insert(self.as_ref().to_string());