feat: Add campaign comments functionality with API support and database migration

migrations/027_campaigns_comments.sql

@@ -0,0 +1,10 @@
+CREATE TABLE IF NOT EXISTS `campaigns_comments` (
+  `id` INT(11) NOT NULL AUTO_INCREMENT,
+  `campaign_id` INT(11) NOT NULL,
+  `comment` TEXT NOT NULL,
+  `date_add` DATE NOT NULL,
+  PRIMARY KEY (`id`),
+  UNIQUE KEY `uk_campaign_comment_date` (`campaign_id`, `date_add`),
+  KEY `idx_campaign_id` (`campaign_id`),
+  CONSTRAINT `FK_campaigns_comments_campaigns` FOREIGN KEY (`campaign_id`) REFERENCES `campaigns` (`id`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;