okenRequestDetails(Config config, String code) {
  this.url = config.tokenUrl;
  this.params = {
    &quot;client_id&quot;: config.clientId,
    &quot;code&quot;: code,
    &quot;redirect_uri&quot;: config.redirectUri,
    &quot;grant_type&quot;: &quot;authorization_code&quot;
  };
  if ( config.clientSecret != null )
    params.putIfAbsent(&quot;client_secret&quot;, () =&gt; config.clientSecret);

  this.headers = {
    &quot;Accept&quot;: &quot;application&#47;json&quot;,
    &quot;Content-Type&quot;: con