UserManager In 2.1 exposed the "purpose" constants, eg. ConfirmEmailTokenPurpose.

We relied on this in order to use userManager.VerifyUserTokenAsync().

Now those constants are gone, and there is a GetChangeEmailTokenPurpose() method in its place, which is protected.

Please make it public, otherwise the verify function is unusable.

(Subclassing just adds an unnecessary mess as this class already conceals a lot of complexity and should be usable as is.)