fix deprecations: use choices_as_values=true and flip content of the choice options

CustomFields/CustomFieldLongChoice.php

@@ -111,8 +111,9 @@ class CustomFieldLongChoice extends AbstractCustomField
         }
 
         return $builder->add(self::KEY, ChoiceType::class, array(
-            'choices' => $choices,
-            'label' => 'Options key'
+            'choices' => array_combine(array_values($choices),array_keys($choices)),
+            'label' => 'Options key',
+            'choices_as_values' => true
         ));
 
     }