A reference that is used to identify a certain authentication.
The reference is obtained when calling BankIdAuthentication
BankIdMobile: If the user is authenticated via mobile BankID
BankIdFile: If the user is authenticated through BankID on file
For more information on the statuses returned: BankID Relying Party Guidelines 12.8.3 https://www.bankid.com/bankid-i-dina-tjanster/rp-info