feat: add questionnaire definitions and their catalog

src/Model/Questionnaire/Section.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace App\Model\Questionnaire;
+
+readonly class Section
+{
+    /**
+     * @param list<Question> $questions
+     */
+    public function __construct(
+        public string $key,
+        public ?string $title,
+        public array $questions,
+    ) {
+    }
+}