Add ability to verify Yubikey second factor, list second factors

Dep: https://github.com/SURFnet/Stepup-Middleware-clientbundle/pull/4

The identity ID is currently hard-coded to `45fb401a-22b6-4829-9495-08b9610c18d4`. This identity must be present in the middleware.

- [ ] Translate translation keys
- [ ] Change back to client@dev-develop
Everything should be valid, there is no list of limiting country codes, at least, that was discussed (tjsut strip any non-digit characters). If you want to be sure, ask Pieter/Joost/Eefje