Add Collabora configuration guide and NullProofValidator class

A new document detailing the configuration steps for enabling Collabora in development has been added. This includes setting up ngrok and configuring both the Collabora and Symfony servers. Furthermore, a new class, NullProofValidator, has been created for validation during the development process. This class always returns true, making it useful for debugging purposes.

src/Bundle/ChillWopiBundle/src/Service/Wopi/NullProofValidator.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Chill\WopiBundle\Service\Wopi;
+
+use ChampsLibres\WopiLib\Contract\Service\ProofValidatorInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Create a proof validator for WOPI services which always return true.
+ *
+ * Useful for debugging purposes.
+ */
+final readonly class NullProofValidator implements ProofValidatorInterface
+{
+    public function isValid(RequestInterface $request): bool
+    {
+        return true;
+    }
+}