MainActivity.kt

private fun createNewUser(email: String, password: String) {
        auth.createUserWithEmailAndPassword(email, password)
            .addOnCompleteListener(this) { task ->
                if (task.isSuccessful) {
                    // Sign in success, update UI with the signed-in user's information
                    val user = auth.currentUser
                    Toast.makeText(
                        baseContext, "Authentication Success.",
                        Toast.LENGTH_SHORT
                    ).show()
                    startHomeActivity()
                } else {
                    // If sign in fails, display a message to the user.
                    Toast.makeText(
                        baseContext, "Authentication failed.",
                        Toast.LENGTH_SHORT
                    ).show()
                }
            }
    }