minor #20459 doc(security): add firewall lazy option (94noni)

This PR was merged into the 6.4 branch.

Discussion
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doc(security): add firewall lazy option

on https://symfony.com/doc/4.x/reference/configuration/security.html, we can see the option anonymous: lazy
on actual maintained version of the doc, https://symfony.com/doc/6.4/reference/configuration/security.html and +
I cant find any reference to lazy

This PR tries to (re)document this option (next to stateless but feel free to challenge)

Please if it was removed on purposes, feel free to close but share a link/PR as I didnt find while searching

Commits
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9eb33c8 Update security.rst

Author: javiereguiluz

reference/configuration/security.rst

@@ -1001,6 +1001,58 @@ the session must not be used when authenticating users:
             // ...
         };
 
+.. _reference-security-lazy:
+
+lazy
+~~~~~~~~~
+
+Firewalls can configure a ``lazy`` boolean option in order to load the user and start the session only
+if the application actually accesses the User object,
+(e.g. via a is_granted() call in a template or isGranted() in a controller or service):
+
+.. configuration-block::
+
+    .. code-block:: yaml
+
+        # config/packages/security.yaml
+        security:
+            # ...
+
+            firewalls:
+                main:
+                    # ...
+                    lazy: true
+
+    .. code-block:: xml
+
+        <!-- config/packages/security.xml -->
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <srv:container xmlns="http://symfony.com/schema/dic/security"
+            xmlns:srv="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
+                http://symfony.com/schema/dic/security
+                https://symfony.com/schema/dic/security/security-1.0.xsd">
+
+            <config>
+                <firewall name="main" lazy="true">
+                    <!-- ... -->
+                </firewall>
+            </config>
+        </srv:container>
+
+    .. code-block:: php
+
+        // config/packages/security.php
+        use Symfony\Config\SecurityConfig;
+
+        return static function (SecurityConfig $security): void {
+            $mainFirewall = $security->firewall('main');
+            $mainFirewall->lazy(true);
+            // ...
+        };
+
 User Checkers
 ~~~~~~~~~~~~~