MAPG-235 new challenge can be created and is prepared

database/migrations/structure/20210510_2000_challenge.sql

@@ -16,7 +16,7 @@ CREATE TABLE `user_in_challenge` (
   `round` smallint(5) signed NOT NULL DEFAULT -1,
   `score` int(10) unsigned NOT NULL DEFAULT 0,
   `time_left` int(10) unsigned,
-  `owner` tinyint(1) NOT NULL DEFAULT 0,
+  `is_owner` tinyint(1) NOT NULL DEFAULT 0,
   PRIMARY KEY (`id`),
   KEY `user_id` (`user_id`),
   KEY `challenge_id` (`challenge_id`),