When attempting to configure a network extension on iOS in the absence of user authorization or MDM provisioning, the call to saveToPreferences() on NEDNSProxyManager fails with an error of code 10 in domain "NEConfigurationErrorDomain". I want to test for this condition in order to present a more helpful message to the user.
However, it appears that NEConfigurationErrorDomain is not declared in any system header. Why not? How do I test for this? Must I resort to a comparison against a string literal "NEConfigurationErrorDomain"?
What other error codes exist in this error domain?