Enhance ResetPasswordAsync & ChangePasswordAsync to detect and repair accidental guest role assignments

[Michael-Herzog]

Original problem: Registered customers lose the registered role and get the guest role.

Fix it with: If the UserManager.ResetPasswordAsync or UserManager.ChangePasswordAsync methods were successful in the IdentityController and email or username are available, then you can assume that it is a registered account and, if necessary, remove an incorrectly assigned guest role and assign the registered role.