Added deprecation warning when using non-DateTimeTypes in TimestampBe…

…havior

src/ORM/Behavior/TimestampBehavior.php

@@ -206,6 +206,7 @@ protected function _updateField($entity, $field, $refreshTimestamp)
         $type = Type::build($columnType);
 
         if (!$type instanceof Type\DateTimeType) {
+            deprecationWarning('TimestampBehavior support for column types other than DateTimeType will be removed in 4.0.');
             $entity->set($field, (string)$ts);
 
             return;