Typescript migration:

* Refactoring of scheduler and jobs to use promises.
* Add "failed" state for tasks.

server/jobs/MonitoringMailsSendingJob.ts

@@ -0,0 +1,20 @@
+import Logger from "../logger";
+import MonitoringService from "../services/monitoringService";
+
+export default {
+    name: 'MonitoringMailsSendingJob',
+    description: 'Sends monitoring emails depending on the monitoring state of nodes retrieved by the NodeInformationRetrievalJob.',
+
+    run: (): Promise<void> => {
+        return new Promise<void>((resolve, reject) => {
+            MonitoringService.sendMonitoringMails((err: any): void => {
+                if (err) {
+                    Logger.tag('monitoring', 'mail-sending').error('Error sending monitoring mails:', err);
+                    return reject(err);
+                }
+
+                resolve();
+            });
+        });
+    }
+};