Allow authentication codes to be autofilled

With iOS 15 and macOS Monterey, Apple is introducing time based authentication code (OTP) into iCloud Keychain. One of the benefits of this is that iOS and macOS will now be able autofill the authentication code, simplifying the user's login experience. Apple's developer documentation describes this as a simple, straightforward change:

AutoFill on iOS and macOS offer to fill verification codes automatically in text fields where you set the content type of the field to a one-time code type. In SwiftUI, set the content type to oneTimeCode with the UITextContentType view modifier. In UIKit, set oneTimeCode to oneTimeCode. In AppKit, set NSTextContentType to oneTimeCode. For web-based text fields, set the HTML attribute on the input element to autocomplete=one-time-code.