person: add validation to relationship to avoid duplicate

src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicate.php

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * 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.
+ */
+
+declare(strict_types=1);
+
+namespace Chill\PersonBundle\Validator\Constraints\Relationship;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * @Annotation
+ */
+class RelationshipNoDuplicate extends Constraint
+{
+    public $message = 'relationship.duplicate';
+
+    public function getTargets()
+    {
+        return self::CLASS_CONSTRAINT;
+    }
+}