https://medium.com/%E5%BD%BC%E5%BE%97%E6%BD%98%E7%9A%84-swift-ios-app-%E9%96%8B%E7%99%BC%E6%95%99%E5%AE%A4/swift-practice-108-firebase-%E5%88%9D%E6%8E%A2-email-%E8%A8%BB%E5%86%8A%E7%99%BB%E5%85%A5%E4%BF%AE%E6%94%B9%E5%AF%86%E7%A2%BC%E5%8A%9F%E8%83%BD-f8da372e17
