mfa integration into selfservice, admin pages and login process

uffd/mfa/templates/auth.html

uffd/mfa/templates/setup.html

uffd/mfa/templates/setup_totp.html

uffd/mfa/views.py

uffd/selfservice/templates/self.html

uffd/session/views.py

uffd/user/templates/user.html