Sliced Invoices Stripe Gateway: move Apple Pay button right to the top of invoice page

functions.php

add_action( 'sliced_invoice_top_bar_left', 'sliced_custom_apple_pay_button', 999 );
add_action( 'sliced_invoice_head', 'sliced_custom_apple_pay_button_scripts' );
function sliced_custom_apple_pay_button() {
	$payments = get_option( 'sliced_payments' );
	if ( ! $payments['stripe_apple_pay'] ) {
		return;
	}
	if( has_term( array( 'paid', 'cancelled' ), 'invoice_status' ) ) {
		return;
	}
	$id            = sliced_get_invoice_id();
	$currency      = sliced_get_invoice_currency( $id );
	$currency_code = $currency && $currency !== 'default' ? $currency : $payments['stripe_currency'];
	$payments_url  = esc_url( get_permalink( (int)$payments['payment_page'] ) );
	?>
	<div class="sliced_gateway_button">
		<button id="sliced-stripe-apple-pay-button" type="button"></button>
	</div>
	<script type="text/javascript">
		Stripe.setPublishableKey( '<?php echo $payments['stripe_publishable'] ?>' );
		Stripe.applePay.checkAvailability(function(available) {
		  if (available) {
			document.getElementById('sliced-stripe-apple-pay-button').style.display = 'block';
		  }
		});
		document.getElementById('sliced-stripe-apple-pay-button').addEventListener('click', beginApplePay);
		function beginApplePay() {
		  var paymentRequest = {
			countryCode: '<?php echo ( $payments['stripe_apple_pay_country'] );?>',
			currencyCode: '<?php echo $currency_code; ?>',
			total: {
			  label: '<?php echo __( 'Invoice', 'sliced-invoices' ) . ' ' . esc_html( sliced_get_invoice_prefix() ) . esc_html( sliced_get_invoice_number() ); ?>',
			  amount: '<?php echo sliced_get_invoice_total_raw( $id ); ?>'
			}
		  };
		  var session = Stripe.applePay.buildSession(paymentRequest,
			function(result, completion) {
			  jQuery.post('<?php echo $payments_url; ?>', {
					sliced_payment_invoice_id: "<?php echo $id; ?>",
					stripeToken: result.token.id,
					sliced_stripe_applepay: "auth"
				}).done(function() {
			  completion(ApplePaySession.STATUS_SUCCESS);
			  window.location.href = '<?php echo add_query_arg( array( 
				'sliced_stripe_applepay' => 'success',
				'sliced_payment_invoice_id' => $id,
			  ), $payments_url ); ?>';
			}).fail(function() {
			  completion(ApplePaySession.STATUS_FAILURE);
			});
		  }, function(error) {
			console.log(error.message);
		  });
		  session.oncancel = function() {
			console.log("User hit the cancel button in the payment window");
		  };
		  session.begin();
		}
	</script>
	<?php
}
function sliced_custom_apple_pay_button_scripts() {
	wp_register_script( 'stripe', 'https://js.stripe.com/v2/', array( 'jquery' ) );
    wp_print_scripts( 'stripe' );
	?>
	<style type="text/css">
		#sliced-stripe-apple-pay-button {
			display: none;
			background-color: black;
			background-image: -webkit-named-image(apple-pay-logo-white);
			background-size: 100% 100%;
			background-origin: content-box;
			background-repeat: no-repeat;
			width: 100px;
			height: 30px;
			margin-top: -1px;
			padding: 10px 0;
			border: none;
			border-radius: 3px;
		}
	</style>
	<?php
}