Add skip button as custom sign-in layout option

[MirecXP]

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Step 1: Are you in the right place?

Yes.

Step 2: Describe your environment

• Android device: any
• Android OS version: any
• Google Play Services version: any
• Firebase/Play Services SDK version: any
• FirebaseUI version: any

Step 3: Describe the problem:

The AuthUI login can be started as part of an onboarding flow. To simplify the UX, we do not want to add a separate onboarding screen for the user to decide whether they want to log in or not. So having a skip button available directly on the sign-in screen would help a lot. The sign in screen can be cancelled by navigating back, but this is not suitable if the sign-in screen is part of some flow.

Steps to reproduce:

1. Create custom sign-in layout (with optional skip/close/cancel button)
2. Create sign-in intent using custom layout
3. Launch sign-in activity using signInIntent

Observed Results:

It is not possible to cancel the launched sign-in activity with a custom button.

Expected Results:

I can use a custom button to cancel the sign in, e.g. Continue without login and I do not need a separate screen for that.

Relevant Code:

         val customSignInLayout: AuthMethodPickerLayout = AuthMethodPickerLayout.Builder(R.layout.onboarding_login_layout)
            .setGoogleButtonId(R.id.google_signin_button)
            .setAppleButtonId(R.id.apple_signin_button)
            .setTosAndPrivacyPolicyId(R.id.tos_link)
            .setSkipButtonId(R.id.skip_signin_button) // <-- this would be very useful
            .build()

        var signInIntent = AuthUI.getInstance()
            .createSignInIntentBuilder()
            .setAvailableProviders(providers)
            .setIsSmartLockEnabled(false)
            .setAlwaysShowSignInMethodScreen(true)
            .setLogo(R.mipmap.ic_launcher)
            .setTosAndPrivacyPolicyUrls(termsUrl, privacyUrl)
            .enableAnonymousUsersAutoUpgrade()
            .setAuthMethodPickerLayout(customSignInLayout)

        launcher.launch(signInIntent.build())  ```