#[derive(Deserialize)]

    #[serde(flatten)]
    pub credentials: Credentials,

    pub credentials: Credentials<Box<str>>,

impl<'de> Deserialize<'de> for AccessToken {
    fn deserialize<D: de::Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
        #[derive(Deserialize)]
        struct AccessToken {
            oauth_token: Box<str>,
            oauth_token_secret: Box<str>,
            user_id: i64,
        }
        AccessToken::deserialize(d).map(|t| Self {
            credentials: Credentials::new(t.oauth_token, t.oauth_token_secret),
            user_id: t.user_id,
        })
    }
}