Build-in support for many different methods instead of only default

[rafsaf]

Expected Behavior

Users should be given an option to setup more methods instead of only primary method.

Current Behavior

When user setup for example yubikey, then in two_factor view sees "Primary method: Use your Yubikey device" and setup for another methods is not possible.

In setup this is clearly visible that this is intentional disabled:

https://github.com/jazzband/django-two-factor-auth/blob/95255bbe714830152e68c9ff2dd09dee4087a2a1/two_factor/views/core.py#L486-L492

However, in login view, many different methods are handled if they exist, for example created in custom form or via admin panel

https://github.com/jazzband/django-two-factor-auth/blob/95255bbe714830152e68c9ff2dd09dee4087a2a1/two_factor/views/core.py#L359-L367

And here how it looks when i add more methods in admin panel:

Possible Solution

Allow users to setup 2fa many times. It's already handled in login so that's for free and could be supported in account and setup views with relatively moderate code changes. Note that I am not sure why is it not a case, maybe there are some non trivial things to consider or breaking changes like that are not acceptable for some reason.

Context

For yubikey setup for eaxmple it totally makes sense and is popular to have 2 or more different keys for example one dedicated to pc, second to laptop and alternatively some backup one.

[moggers87]

Sounds good, we would ideally want this either as part of or after #347