Multi-stage otp support

[zapotah]

When you have more than one factor for otp, openforticlient has no way to input a second (or third) factor. For example when using ie. radius authentication in the backend for fortigate where you send multiple access-challenge messages (for ie. okta so you can choose which second factor to use which in the case of openforticlient is the first "otp" and then it expects the actual second factor.). This results in two rounds of "otp" responses which openforticlient cannot do at the moment.