Enable endusers to use StrongKey FIDO Server (SKFS) for Native apps for iOS 15 and less

While StrongKey iOS Demo does work on iOS 15 and up, the Passkey API which it relies on is only available to the general public from iOS 16 and up and that's why it works for iOS 16 for the end users.

For iOS 15 and less, passkeys were enabled for browser based applications. However, for native apps in iOS 15 and less, Passkeys needs to be enabled by permitting developer mode in order to use them in applications.

However, SKFS can still be used on iOS 15 and less native apps through the browser. To do that, use a ASWebAuthenticationSession API to open a browser sheet in the app, complete the FIDO Authentication and return the JWT from SKFS to the application using a callback URL.