Issue #518
let userDefaults = UserDefaults(suiteName: suiteName)
userDefaults.removePersistentDomain(forName: suiteName)
https://developer.apple.com/documentation/foundation/userdefaults/1417339-removepersistentdomain
Calling this method is equivalent to initializing a user defaults object with init(suiteName:) passing domainName, and calling the removeObject(forKey:) method on each of its keys.