feat(01-purchase-data-layer): add post-payment purchase data layer

Phase 1 complete:

- move purchase event to order confirmation after successful payment

- add backend purchase payload builder for transaction and ticket lines

- remove premature purchase push from przelewy24 redirect view

templates/tickets/przelewy24.php

@@ -43,27 +43,7 @@ if($this->settings['p24']['sandbox']) {
 </form>
 
 <script type="text/javascript">
-  dataLayer.push({ ecommerce: null });
-  dataLayer.push({
-    event: "purchase",
-    ecommerce: {
-      transaction_id: "<?= $this -> order['id'];?>",
-      value: <?= str_replace( ',', '.', $this -> order['order_price'] );?>,
-      currency: "PLN",
-      shipping: 0,
-      items: [
-        <? foreach ( $this -> order['tickets'] as $ticket ):?>
-        {
-          'id': <?= (int)$ticket['product_id'];?>,
-          'name': '<?= $ticket['name'];?>',
-          'quantity': <?= $ticket['quantity'];?>,
-          'price': <?= $ticket['price'];?>
-        }<? if ( $ticket != end( $this -> order['tickets'] ) ) echo ',';?>
-      <? endforeach;?>
-      ]
-    }
-  });
   $( document ).ready( function() {
     $( "#form_data" ).submit();
   });
-</script>
+</script>