add validation to accompanying periods

src/Bundle/ChillPersonBundle/Validator/Constraints/AccompanyingPeriod/ResourceDuplicateCheck.php

@@ -0,0 +1,16 @@
+<?php
+declare(strict_types=1);
+
+namespace Chill\PersonBundle\Validator\Constraints\AccompanyingPeriod;
+
+use Symfony\Component\Validator\Constraint;
+
+
+/**
+ * @Annotation
+ */
+class ResourceDuplicateCheck extends Constraint
+{
+    public $message = '{{ name }} is already associated to this accompanying course.';
+}
+