Show secret on setup.html to allow for manual entry for multiple yubikeys & other devices

[9mido]

This PR allows for users to manually enter the same secret key for multiple mobile devices or multiple yubikey devices using the downloadable yubikey authenticator app in case the user loses one of their yubikeys or mobile devices. In other words, it allows a user to create multiple yubikey or mobile 2FA devices to use for their one online account. By creating backup yubikeys or mobile devices with the same OTP secret on them, it decreases the chances of a user not being able to log into their account if they lose one or more of their yubikey or mobile devices.

[simonkern]

There is btw no need to edit the view, device is already available in the context. You can achieve this with a template filter and a minor change to the template:

templatetags/b32encode.py

from base64 import b32encode as b32enc

from django import template

register = template.Library()

@register.filter()
def b32encode(value):
    return b32enc(value).decode('utf-8')

and then in the template:

allauth_2fa/setup.html

{% load b32encode %}
...
...
...
Secret: {{ view.device.bin_key|b32encode }}

[9mido]

@simonkern Thanks for this. I am fine with whatever method (yours or mine) the maintainer of django-allauth-2fa chooses to use. I give permission to the maintainer to close this PR and make one themselves with this feature with whatever method they desire. Hopefully we can see this feature in the main branch soon.