Merge branch '5.4' into 6.3

* 5.4:
  [Translation] Add information about custom providers

Author: javiereguiluz

reference/dic_tags.rst

@@ -1208,6 +1208,49 @@ This is the name that's used to determine which dumper should be used.
         $container->register(JsonFileDumper::class)
             ->addTag('translation.dumper', ['alias' => 'json']);
 
+.. _reference-dic-tags-translation-provider-factory:
+
+translation.provider_factory
+----------------------------
+
+**Purpose**: to register a factory related to custom translation providers
+
+When creating custom :ref:`translation providers <translation-providers>`, you
+must register your factory as a service and tag it with ``translation.provider_factory``:
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        services:
+            App\Translation\CustomProviderFactory:
+                tags:
+                    - { name: translation.provider_factory }
+
+    .. code-block:: xml
+
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <container xmlns="http://symfony.com/schema/dic/services"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xsi:schemaLocation="http://symfony.com/schema/dic/services
+                https://symfony.com/schema/dic/services/services-1.0.xsd">
+
+            <services>
+                <service id="App\Translation\CustomProviderFactory">
+                    <tag name="translation.provider_factory"/>
+                </service>
+            </services>
+        </container>
+
+    .. code-block:: php
+
+        use App\Translation\CustomProviderFactory;
+
+        $container
+            ->register(CustomProviderFactory::class)
+            ->addTag('translation.provider_factory')
+        ;
+
 .. _reference-dic-tags-twig-extension:
 
 twig.extension

translation.rst

@@ -743,6 +743,19 @@ now use the following commands to push (upload) and pull (download) translations
     # check out the command help to see its options (format, domains, locales, intl-icu, etc.)
     $ php bin/console translation:pull --help
 
+Creating Custom Providers
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In addition to using Symfony's built-in translation providers, you can create
+your own providers. To do so, you need to create two classes:
+
+#. The first class must implement :class:`Symfony\\Component\\Translation\\Provider\\ProviderInterface`;
+#. The second class needs to be a factory which will create instances of the first class. It must implement
+:class:`Symfony\\Component\\Translation\\Provider\\ProviderFactoryInterface` (you can extend :class:`Symfony\\Component\\Translation\\Provider\\AbstractProviderFactory` to simplify its creation).
+
+After creating these two classes, you need to register your factory as a service
+and tag it with :ref:`translation.provider_factory <reference-dic-tags-translation-provider-factory>`.
+
 .. _translation-locale:
 
 Handling the User's Locale