minor #12731 Add cookbook with how to change tax address (arti0090)

This PR was merged into the 1.9 branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Branch?         | 1.9
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | same as #12724 but on 1.9 branch
| License         | MIT

Opened new PR as old one was making a lot of merge conflicts.

Commits
-------

934749e Add cookbook with how to change tax address

docs/cookbook/index.rst

@@ -150,3 +150,13 @@ Frontend
     frontend/webpack.rst
 
 .. include:: /cookbook/frontend/map.rst.inc
+
+Taxation
+--------
+
+.. toctree::
+    :hidden:
+
+    taxation/customize-tax-by-address
+
+.. include:: /cookbook/taxation/map.rst.inc

docs/cookbook/taxation/customize-tax-by-address.rst

@@ -0,0 +1,49 @@
+How to configure tax rates to be based on shipping address?
+===========================================================
+
+The default configuration of Sylius tax calculation is based on billing address but there are situations where we would
+like to use a shipping address to be used in this process. This may be useful to anyone who uses Sylius in European Union
+as from 1st July 2021 the new taxation rules will be applied.
+
+.. note::
+
+    You can learn more about new EU taxation rules `here <https://ec.europa.eu/taxation_customs/business/vat/modernising-vat-cross-border-ecommerce_en>`_.
+
+To change the way how the taxes are calculated; by billing or by shipping address, you need to override the service called
+``OrderTaxesProcessor.php`` from ``Sylius/Component/Core/OrderProcessing``.
+
+First let's copy code from original Processor to our service
+from ``%kernel.project_dir%/vendor/sylius/sylius/src/Sylius/Component/Core/OrderProcessing/OrderTaxesProcessor.php`` to ``src/OrderProcessing/OrderTaxesProcessor.php``
+
+Then register our new service:
+
+.. code-block:: yaml
+
+    # app/config/services.yaml
+        App\OrderProcessing\OrderTaxesProcessor:
+        arguments:
+            - '@sylius.provider.channel_based_default_zone_provider'
+            - '@sylius.zone_matcher'
+            - '@sylius.registry.tax_calculation_strategy'
+        tags:
+            - { name: sylius.order_processor, priority: 10 }
+
+Now we need to change the method ``getTaxZone`` to be using the shipping address:
+
+.. code-block:: php
+
+    //...
+    private function getTaxZone(OrderInterface $order): ?ZoneInterface
+    {
+        $shippingAddress = $order->getShippingAddress();
+        $zone = null;
+
+        if (null !== $shippingAddress) {
+            $zone = $this->zoneMatcher->match($shippingAddress, Scope::TAX);
+        }
+
+        return $zone ?: $this->defaultTaxZoneProvider->getZone($order);
+    }
+    //...
+
+And with this change, the way how taxes are calculated will be based on shipping address.

docs/cookbook/taxation/map.rst.inc

@@ -0,0 +1 @@
+* :doc:`/cookbook/taxation/customize-tax-by-address`