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/goalert.js

@@ -3,21 +3,20 @@ const axios = require("axios");
 const { UP } = require("../../src/util");
 
 class GoAlert extends NotificationProvider {
-
     name = "GoAlert";
 
     /**
      * @inheritdoc
      */
     async send(notification, msg, monitorJSON = null, heartbeatJSON = null) {
-        let okMsg = "Sent Successfully.";
+        const okMsg = "Sent Successfully.";
+
         try {
-            let closeAction = "close";
             let data = {
                 summary: msg,
             };
             if (heartbeatJSON != null && heartbeatJSON["status"] === UP) {
-                data["action"] = closeAction;
+                data["action"] = "close";
             }
             let headers = {
                 "Content-Type": "multipart/form-data",
@@ -27,7 +26,6 @@ class GoAlert extends NotificationProvider {
             };
             await axios.post(`${notification.goAlertBaseURL}/api/v2/generic/incoming?token=${notification.goAlertToken}`, data, config);
             return okMsg;
-
         } catch (error) {
             let msg = (error.response.data) ? error.response.data : "Error without response";
             throw new Error(msg);