Query string parameter 'type' is now enforced by the api

+ Flag is literally called 'type'

json-api/migrations/2020-07-06-022319_messages/up.sql

@@ -3,7 +3,7 @@ CREATE TABLE IF NOT EXISTS `messages`(
 	`id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
 	`time` BIGINT NOT NULL,
 	`content` VARCHAR(4096) NOT NULL,
-	`content_type` VARCHAR NOT NULL,
+	`content_type` VARCHAR(10) NOT NULL,
 	`author_id` BIGINT UNSIGNED NOT NULL,
 	`channel_id` BIGINT UNSIGNED NOT NULL,
 	PRIMARY KEY (`id`),