Prepend hostname to notification message

If multiple instances of uptime-kuma are deployed to cross-check each other and/or in different environments (say ipv4+ipv6 and ipv6 only), and only one or some of the instances fire notificationsm, it is tricky to figure out which specific environment is experiencing the outage. Explicitly setting unique hostnames and prepending it to the message will help in these scenarios.

Signed-off-by: Sid Sun <sids@Sids-MacBook.local>

README.md

@@ -40,7 +40,7 @@ It is a temporary live demo, all data will be deleted after 10 minutes. Sponsore
 ### 🐳 Docker
 
 ```bash
-docker run -d --restart=always -p 3001:3001 -v uptime-kuma:/app/data --name uptime-kuma louislam/uptime-kuma:1
+docker run -d --restart=always -p 3001:3001 -v uptime-kuma:/app/data --hostname uptime-kuma --name uptime-kuma louislam/uptime-kuma:1
 ```
 
 Uptime Kuma is now running on <http://0.0.0.0:3001>.
@@ -52,7 +52,7 @@ Uptime Kuma is now running on <http://0.0.0.0:3001>.
 > If you want to limit exposure to localhost (without exposing port for other users or to use a [reverse proxy](https://github.com/louislam/uptime-kuma/wiki/Reverse-Proxy)), you can expose the port like this:
 > 
 > ```bash
-> docker run -d --restart=always -p 127.0.0.1:3001:3001 -v uptime-kuma:/app/data --name uptime-kuma louislam/uptime-kuma:1
+> docker run -d --restart=always -p 127.0.0.1:3001:3001 -v uptime-kuma:/app/data --hostname uptime-kuma --name uptime-kuma louislam/uptime-kuma:1
 > ```
 
 ### 💪🏻 Non-Docker

compose.yaml

@@ -1,5 +1,6 @@
 services:
   uptime-kuma:
+    hostname: uptime-kuma
     image: louislam/uptime-kuma:1
     volumes:
       - ./data:/app/data

server/model/monitor.js

@@ -24,6 +24,7 @@ const { CookieJar } = require("tough-cookie");
 const { HttpsCookieAgent } = require("http-cookie-agent/http");
 const https = require("https");
 const http = require("http");
+const os = require('os');
 
 const rootCertificates = rootCertificatesFingerprints();
 
@@ -1288,7 +1289,7 @@ class Monitor extends BeanModel {
                 text = "🔴 Down";
             }
 
-            let msg = `[${monitor.name}] [${text}] ${bean.msg}`;
+            let msg = `[${os.hostname()}] [${monitor.name}] [${text}] ${bean.msg}`;
 
             for (let notification of notificationList) {
                 try {