page.go
func JoinPage(url string, options ...Option) *Page {
	pageOptions := config{}.Merge(options)
	session := api.NewWithClient(url, pageOptions.HTTPClient)
	return newPage(session)
}
func JoinPage(url string, options ...Option) *Page {
	pageOptions := config{}.Merge(options)
	session := api.NewWithClient(url, pageOptions.HTTPClient)
	return newPage(session)
}
// JoinPage creates a Page using existing session URL. This method takes Options
// but respects only the HTTPClient Option if provided.