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/ntfy.js

@@ -3,14 +3,14 @@ const axios = require("axios");
 const { DOWN, UP } = require("../../src/util");
 
 class Ntfy extends NotificationProvider {
-
     name = "ntfy";
 
     /**
      * @inheritdoc
      */
     async send(notification, msg, monitorJSON = null, heartbeatJSON = null) {
-        let okMsg = "Sent Successfully.";
+        const okMsg = "Sent Successfully.";
+
         try {
             let headers = {};
             if (notification.ntfyAuthenticationMethod === "usernamePassword") {
@@ -31,7 +31,7 @@ class Ntfy extends NotificationProvider {
                     "priority": notification.ntfyPriority,
                     "tags": [ "test_tube" ],
                 };
-                await axios.post(`${notification.ntfyserverurl}`, ntfyTestData, { headers: headers });
+                await axios.post(notification.ntfyserverurl, ntfyTestData, { headers: headers });
                 return okMsg;
             }
             let tags = [];
@@ -70,7 +70,7 @@ class Ntfy extends NotificationProvider {
                 data.icon = notification.ntfyIcon;
             }
 
-            await axios.post(`${notification.ntfyserverurl}`, data, { headers: headers });
+            await axios.post(notification.ntfyserverurl, data, { headers: headers });
 
             return okMsg;