[iOS Only] Support Passcode Fallback Natively

[ianoshorty]

This change simply allows iOS to use Passcode fallback if its available and needed. It does not change the behaviour of FaceID / TouchID in any other way, and only uses Passcode as a fallback. Some extended discussion is at #34 - which notes you may wish to enable a switch to enable / disable this - but this PR is enough for us.

Happy for it to be merged if you like.

[EyMaddis]

bump @naoufal

[zibs]

@naoufal This works and looks good to me. I'm okay with the native fallback, we should just add something to the readme since this might change existing user's expectations.

[wanschi]

Is there a reason why this is not merged?

[ianoshorty]

I've updated this PR to merge all recent changes and still support fallback to passcode auth. If this isn't merged in a few weeks, I will close the PR as I'm guessing it isn't needed.

[zibs]

Hey, thanks for the PR @ianoshorty - I'll give it a run through this week to make sure everything checks out. Let's add that optional config option to enable this feature though, since we don't want to change existing functionality. Do you mind doing that? if not, feel free to allow edits from maintainers from this PR and I'll go in an add it.

[ianoshorty]

I wont be able to further update the PR till next week. I'd be happy to take a look then though to add the config option if its needed.

[ianoshorty]

@zibs As requested, I've added a config option passcodeFallback, default false, which when true will utilise keypad based passcode entry. This is documented in the readme.

Hope thats everything!

[anandwahed]

@zibs any idea when this will be merged in master ?

[zibs]

Thanks for the bump! I just need to test it and make sure it's good to go and then will merge and release asap. I can try my darn'dest to get to on the weekend if not sooner.

[zibs]

Works! Thanks! I'm going to bump the version to 4.2.

[randomor]

Is this system passcode fallback still being presented? I'm not seeing anything on iPhone X and only saw an error in the catch callback... Would appreciate some pointers on this.