Update ring to 0.14, jwt to 6.0, and u2f

src/auth.rs

@@ -40,7 +40,6 @@ fn decode_jwt<T: DeserializeOwned>(token: &str, issuer: String) -> Result<T, Err
     let validation = jsonwebtoken::Validation {
         leeway: 30, // 30 seconds
         validate_exp: true,
-        validate_iat: false, // IssuedAt is the same as NotBefore
         validate_nbf: true,
         aud: None,
         iss: Some(issuer),