docs: make discoverFilters() deprecated

Author: kenjis

system/Filters/Filters.php

@@ -125,6 +125,8 @@ public function __construct($config, RequestInterface $request, ResponseInterfac
      *
      * Sample :
      * $filters->aliases['custom-auth'] = \Acme\Blob\Filters\BlobAuth::class;
+     *
+     * @deprecated 4.4.2 Use Registrar instead.
      */
     private function discoverFilters(): void
     {

user_guide_src/source/general/modules.rst

@@ -163,6 +163,13 @@ In that case, see :ref:`routing-priority`.
 Filters
 =======
 
+.. deprecated:: 4.4.2
+
+.. note:: This feature is deprecated. Use :ref:`registrars` instead like the
+    following:
+
+    .. literalinclude:: modules/015.php
+
 By default, :doc:`filters <../incoming/filters>` are automatically scanned for within modules.
 It can be turned off in the **Modules** config file, described above.
 

user_guide_src/source/general/modules/015.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace CodeIgniter\Shield\Config;
+
+use CodeIgniter\Shield\Filters\SessionAuth;
+use CodeIgniter\Shield\Filters\TokenAuth;
+
+class Registrar
+{
+    /**
+     * Registers the Shield filters.
+     */
+    public static function Filters(): array
+    {
+        return [
+            'aliases' => [
+                'session' => SessionAuth::class,
+                'tokens'  => TokenAuth::class,
+            ],
+        ];
+    }
+}