开放平台OAuth

• 例子：

    OpenOAuth2s openOAuth2s = OpenOAuth2s.defaultOpenOAuth2s();
    //或者：
    AppSetting appSetting = new AppSetting("appId", "secret");
    OpenOAuth2s openOAuth2s = OpenOAuth2s.with(appSetting);
  
    //生成授权链接,默认scope: snsapi_base
    openOAuth2s.authenticationUrl("url");
    
    //生成授权链接,指定scope: snsapi_base or snsapi_userinfo
    openOAuth2s.authenticationUrl("url", "scope");
  
    //生成授权链接,指定scope，指定state
    openOAuth2s.authenticationUrl("url", "scope", "state");
    
    //获取AccessToken
    AccessToken accessToken = openOAuth2s.getAccessToken("code");
  
    //获取用户信息
    OpenUser user = openOAuth2s.userInfo(accessToken, "openId");