Enable Multifactor authentication

[doginthehat]

Feature request

Firebase (through Google Identity Platform) supports Multifactor authentication or 2fa.

Currently only phone is available as a second factor.

The native Firebase SDKs support these method but FirebaseX currently doesn't expose the SDK methods required.

Here's an example for iOS SDK https://cloud.google.com/identity-platform/docs/ios/mfa#objective-c_2

To enable that, FirebaseX would need to expose more native Firebase functions to the JS bridge

The pattern for enrollement is:

1. Start a MFa session
2. Send number verification request, get a verificationID back
3. Request code input from user
4. Match code with verificationID
5. Enroll

For example, on iOS we would need those:

- (void)getSessionWithCompletion:(nullable void (^)(FIRMultiFactorSession *_Nullable credential,
                                                    NSError *_Nullable error))completion;

- (void)verifyPhoneNumber:(NSString *)phoneNumber
               UIDelegate:(nullable id<FIRAuthUIDelegate>)UIDelegate
       multiFactorSession:(nullable FIRMultiFactorSession *)session
               completion:(nullable FIRVerificationResultCallback)completion;

- (FIRPhoneAuthCredential *)credentialWithVerificationID:(NSString *)verificationID
                                        verificationCode:(NSString *)verificationCode;

FIRMultiFactorAssertion *assertion = [FIRPhoneMultiFactorGenerator assertionWithCredential:credential];


- (void)enrollWithAssertion:(FIRMultiFactorAssertion *)assertion
                displayName:(nullable NSString *)displayName
                 completion:(nullable void (^)(NSError *_Nullable error))completion;

I haven't looked into Android SDK but would be similar pattern/apis.

Thank you 🙏

[dpa99c]

Implemented in v16.0.0