Reauthentication documentation

[Vagab]

resolves #24

[Vagab]

@tcannonfodder while working on this pr, I've stumbled a question:
I see we're relying on the users defining the relying_party method(pun intended), which should return the new relying party. However, in WebAuthn::StrategyHelpers there's a defined relying_party which looks into the env. Since the users are going to define the relying_party themselves, what's the purpose of including it in helpers?

[tcannonfodder]

IIRC, the Warden strategy operates in an entirely different context, so it doesn't have access to the relying_party method the user defines. Instead, it pulls from the request's env hash to get the relying party that the user set up as part of the request's preamble

[Vagab]

I think normally that's exactly right, but in our case it seems that the relying_party method is actually included into the controller. Moreover, if you remove the relying_party concern from the template you will get a confusing error:

NameError (undefined local variable or method `env' for #<Users::SessionsController:0x00000000010180>)

which happens bc the #env method was deprecated in rails 5. But that's not the point, the point is that when the relying_party method is missing from the controller, the warden will call it's own relying_party method, and since it's clear that the end user has to define the relying_party method themselves, the warden's relying_party method's purpose eludes me.
So with the limited time I had to look at the code I propose the following changes, lmk wyt:

1. Rename the relying_party method in Warden::WebAuthn
2. Maybe alias env to be request.env? Or am I missing smth? Taking a quick look at the warden code, the env is supposed to be exactly rack env, so I think either changing env to request.env or just alias_method :env, :request_env if we need it to be precisely env should be good.

[tcannonfodder]

I'm digging into the code, for both; and an alternative is breaking up the Warden::WebAuthn::StrategyHelpers; or adjusting how it's used in devise-passkeys

Technically; the env is a special variable passed to strategies when they're initialized: https://github.com/wardencommunity/warden/blob/88d2f59adf5d650238c1e93072635196aea432dc/lib/warden/strategies/base.rb#L45

What's happening here is that we're including Warden::WebAuthn::StrategyHelpers in non-strategy parts of the codebase because the module has useful helper method, and the idea is:

If we inherit from the StrategyHelpers to get the authentication_challenge_key, parsed_credential, relying_party_key, etc. ; we'll help maintain consistency between the two Rack middlewares.

However, obviously that approach has some sharp edges. From Warden::WebAuthn's perspective; we want to keep the relying_party method the way it is, because in the context of that gem, the naming convention makes sense.

But breaking stuff up too much makes the code a maintenance nightmare. I'm going to see about finding a middle ground; possibly with a Warden::WebAuthn::RackHelpers that is automatically included when StrategyHelpers is included

[tcannonfodder]

Just waiting on CI, but this is good to go when green!

Thanks so much for doing the heavy lifting here; there were only a few edits & symbol references to add. And we made some great refactors through the process 💪🎉💪

Looking forward to the next PR!