@RequiresApi(21)
        public Builder addInvisibleAction(Action action) {
            mInvisibleActions.add(action);
            return this;
        }
Add an invisible action to this notification. Invisible actions are never displayed by
the system, but can be retrieved and used by other application listening to
system notifications. Invisible actions are supported from Android 4.4.4 (API 20) and can
be retrieved using {@link NotificationCompat#getInvisibleActions(Notification)}.

@param action The action to add.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/compat/NotificationCompat.java