FactorGrantedAuthority is a GrantedAuthority that also contains a Timestamp issuedAt property.

This is similar to gh-17864 but I'd prefer to use a specific type for factors since we will likely add additional properties like clientIpAddress. Additionally, properties like expiresAt do not make sense for the FactorGrantedAuthority because it is up to the authorization rule to determine if access is granted given the issuedAt property.