feat(automations): add per-host maintenance mode and recurring schedules (#1521)

plugins/automations/migrations/mysql/0003_host_maintenance.sql

@@ -0,0 +1,12 @@
+-- automations 0003: host_maintenance
+-- Generated by termix-plugin migrations. Review before committing.
+
+CREATE TABLE IF NOT EXISTS `p_automations_host_maintenance` (
+  `id` int AUTO_INCREMENT PRIMARY KEY,
+  `user_id` varchar(255) NOT NULL,
+  `host_id` int NOT NULL,
+  `state` text NOT NULL,
+  FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE,
+  FOREIGN KEY (`host_id`) REFERENCES `ssh_data` (`id`) ON DELETE CASCADE
+);
+CREATE UNIQUE INDEX `maintenance_host_owner` ON `p_automations_host_maintenance` (`user_id`, `host_id`);