Added reason option into the configuration

Author: sebprt

src/Plugin/Filtering/Configuration/Reject.php

@@ -28,6 +28,14 @@ public function getConfigTreeBuilder(): TreeBuilder
                             ->then(asExpression())
                         ->end()
                     ->end()
+                    ->scalarNode('reason')
+                        ->isRequired()
+                        ->cannotBeEmpty()
+                        ->validate()
+                            ->ifTrue(isExpression())
+                            ->then(asExpression())
+                        ->end()
+                    ->end()
                 ->end()
             ->end()
         ;