fix(apple-sign-in): return identityToken, authorizationCode as String not native iOS Object

[przemyslawturek]

Description

Fix iOS identityToken, authorizationCode returning native object instead of string value.

Problem

On iOS, SignIn.signIn(options) returns identityToken, authorizationCode object instead of strings.
typeof identityToken is object not a string and should be converted before used in BE
typeof authorizationCode is object not a string and should be converted before used in BE

Solution

Use .toString() method after decoding data

Testing

• Tested on iOS device iOS 16.7.12 and simulator iOS 17.5 also iOS 18.0
• Verified identityToken, authorizationCode are now JavaScripts strings
• Sign-in flow works correctly sending token to BE

Platforms affected

• iOS
• Android