Chore: General notification reformatting (#3182)

- I unified where in file the name of `NotificationProvider.name` is placed
- I made sure that all the providers adhere to the signature of `NotificationProvider.send()`
- I made sure that all the providers use `okMsg` if returning success messages directly from the function.
  Here a discussion should be had:
  Should this be refactored into a constant of `NotificationProvider`? I could imagine that `NotificationProvider.SENDING_SUCCESSFULL`  could be a suitable alternative.
- I made sure all providers have the URL they `POST`/`GET` to be extraced into a variable.
  => refactored this way due to Nelsons suggestion

server/notification-providers/grafana-oncall.js

@@ -3,19 +3,18 @@ const axios = require("axios");
 const { DOWN, UP } = require("../../src/util");
 
 class GrafanaOncall extends NotificationProvider {
-
     name = "GrafanaOncall";
 
     /**
      * @inheritdoc
      */
     async send(notification, msg, monitorJSON = null, heartbeatJSON = null) {
+        const okMsg = "Sent Successfully.";
 
         if (!notification.GrafanaOncallURL) {
             throw new Error("GrafanaOncallURL cannot be empty");
         }
 
-        let okMsg = "Sent Successfully.";
         try {
             if (heartbeatJSON === null) {
                 let grafanaupdata = {
@@ -23,10 +22,7 @@ class GrafanaOncall extends NotificationProvider {
                     message: msg,
                     state: "alerting",
                 };
-                await axios.post(
-                    notification.GrafanaOncallURL,
-                    grafanaupdata
-                );
+                await axios.post(notification.GrafanaOncallURL, grafanaupdata);
                 return okMsg;
             } else if (heartbeatJSON["status"] === DOWN) {
                 let grafanadowndata = {
@@ -34,10 +30,7 @@ class GrafanaOncall extends NotificationProvider {
                     message: heartbeatJSON["msg"],
                     state: "alerting",
                 };
-                await axios.post(
-                    notification.GrafanaOncallURL,
-                    grafanadowndata
-                );
+                await axios.post(notification.GrafanaOncallURL, grafanadowndata);
                 return okMsg;
             } else if (heartbeatJSON["status"] === UP) {
                 let grafanaupdata = {
@@ -45,10 +38,7 @@ class GrafanaOncall extends NotificationProvider {
                     message: heartbeatJSON["msg"],
                     state: "ok",
                 };
-                await axios.post(
-                    notification.GrafanaOncallURL,
-                    grafanaupdata
-                );
+                await axios.post(notification.GrafanaOncallURL, grafanaupdata);
                 return okMsg;
             }
         } catch (error) {