Takes two parameters: Username, GroupTypes
The User parameter accepts any one of the following:
GroupTypes: The list of Group Types to check can be separated by any of the following: $I, $CrLf, $Tab, or a comma.
If GroupTypes is set to a * it will return True for any valid user. If GroupTypes is blank or set to -* it will always return True, without validating the user.
Because IsGroupType$ does not consider if a user is currently logged in, it must never be used in place of SessionIsGroupType$ for validating the credentials of a logged-in user. The IsGroupType$ function exists for checking on the permissions of a user via API calls that are authenticating the user another way, and to check group membership while enforcing security on certain actions while not logged in, such as implementing the Setup table value of Cnw.LoginNoEmailGroupTypes.