minor #20289 Document the new SYMFONY_* env vars (javiereguiluz)

This PR was squashed before being merged into the 7.2 branch.

Discussion
----------

Document the new `SYMFONY_*` env vars

Fixes #20252.

Commits
-------

e14e05f Document the new `SYMFONY_*` env vars

Author: javiereguiluz

deployment/proxies.rst

@@ -22,7 +22,11 @@ Solution: ``setTrustedProxies()``
 ---------------------------------
 
 To fix this, you need to tell Symfony which reverse proxy IP addresses to trust
-and what headers your reverse proxy uses to send information:
+and what headers your reverse proxy uses to send information.
+
+You can do that by setting the ``SYMFONY_TRUSTED_PROXIES`` and ``SYMFONY_TRUSTED_HEADERS``
+environment variables on your machine. Alternatively, you can configure them
+using the following configuration options:
 
 .. configuration-block::
 
@@ -93,6 +97,11 @@ and what headers your reverse proxy uses to send information:
     ``private_ranges`` as a shortcut for private IP address ranges for the
     ``trusted_proxies`` option was introduced in Symfony 7.1.
 
+.. versionadded:: 7.2
+
+    Support for the ``SYMFONY_TRUSTED_PROXIES`` and ``SYMFONY_TRUSTED_HEADERS``
+    environment variables was introduced in Symfony 7.2.
+
 .. caution::
 
     Enabling the ``Request::HEADER_X_FORWARDED_HOST`` option exposes the

reference/configuration/framework.rst

@@ -198,7 +198,12 @@ named ``kernel.http_method_override``.
 trust_x_sendfile_type_header
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-**type**: ``boolean`` **default**: ``false``
+**type**: ``boolean`` **default**: ``%env(bool:default::SYMFONY_TRUST_X_SENDFILE_TYPE_HEADER)%``
+
+.. versionadded:: 7.2
+
+    In Symfony 7.2, the default value of this option was changed from ``false`` to the
+    value stored in the ``SYMFONY_TRUST_X_SENDFILE_TYPE_HEADER`` environment variable.
 
 ``X-Sendfile`` is a special HTTP header that tells web servers to replace the
 response contents by the file that is defined in that header. This improves
@@ -450,7 +455,12 @@ in debug mode.
 trusted_hosts
 ~~~~~~~~~~~~~
 
-**type**: ``array`` | ``string`` **default**: ``[]``
+**type**: ``array`` | ``string`` **default**: ``['%env(default::SYMFONY_TRUSTED_HOSTS)%']``
+
+.. versionadded:: 7.2
+
+    In Symfony 7.2, the default value of this option was changed from ``[]`` to the
+    value stored in the ``SYMFONY_TRUSTED_HOSTS`` environment variable.
 
 A lot of different attacks have been discovered relying on inconsistencies
 in handling the ``Host`` header by various software (web servers, reverse