“请求”是在omiauth-wsfed gem中创建的对象吗？

Question

我使用的是omniauth-wsfed gem，根据documentation，我看到我应该在sessions_controller上添加一些代码，如下所示：

def create
  auth = request.env["omniauth.auth"]  
  auth.uid # Gets the UID value of the user that has just signed in
  # Create a session, redirect etc
end

我在omniauth-wsfed gem及其依赖项中同时查找了请求（对象）和环境（方法），但都失败了。谁能解释我omniauth-wsfed gem或其依赖项如何以及在何处“读取”请求对象并在其上应用env方法？