FPVCallbacks.kt

override fun onVerificationCompleted(credential: PhoneAuthCredential?) {
        if (credential != null && storedVerificationId != null)
            signInWithPhoneAuthCredential(credential)
        else {
            Toast.makeText(
                this,
                "Something went wrong, please try later.",
                Toast.LENGTH_LONG).show()
            finish()
        }
    }


override fun onVerificationFailed(exception: FirebaseException?) {
        Toast.makeText(
            this, "Something went wrong, try again later please.",
            Toast.LENGTH_LONG).show()
        finish()
}

override fun onCodeSent(
        verificationId: String?,
        token: PhoneAuthProvider.ForceResendingToken?
    ) {
        storedVerificationId = verificationId!!
        resendToken = token!!
    }