extension OAuth2Base {
    func request(forURL url: URL, cachePolicy: NSURLRequest.CachePolicy = .reloadIgnoringLocalCacheData) -> URLRequest {
        var req = URLRequest(url: url, cachePolicy: cachePolicy, timeoutInterval: 20)
        try? req.sign(with: self)
        return req
    }
}

extension URLRequest {
    public mutating func sign(with oauth2: OAuth2Base) throws {
        guard let idToken = oauth2.clientConfig.idToken, !idToken.isEmpty else {
            throw OAuth2Error.noAccessToken
        }
        setValue("Bearer \(idToken)", forHTTPHeaderField: "Authorization")
    }
}