Implement secure random password generation and fix permission issues

CloudronManifest.json

@@ -5,7 +5,7 @@
   "description": "Elasticsearch is a distributed, open source search and analytics engine for all types of data. This package is designed for internal use only.",
   "tagline": "Distributed search and analytics engine",
   "version": "1.0.0",
-  "healthCheckPath": "/",
+  "healthCheckPath": "/_cluster/health?pretty",
   "httpPort": 9200,
   "manifestVersion": 2,
   "website": "https://www.elastic.co/elasticsearch/",
@@ -24,13 +24,13 @@
     "database"
   ],
   "minBoxVersion": "7.0.0",
-  "memoryLimit": 1073741824,
-  "postInstallMessage": "Elasticsearch is now installed and available for internal use only. You can access it using http://localhost:9200 from within other Cloudron apps.",
+  "memoryLimit": 4294967296,
+  "postInstallMessage": "Elasticsearch is now installed and available for internal use only. You can access it using http://localhost:9200 from within other Cloudron apps.\n\nUsername: elastic\nPassword: A secure random password has been generated and stored in /app/data/credentials.txt. You can check it in the app logs or by accessing the app container.",
   "multiDomain": false,
   "tcpPorts": {
     "9300": {
       "title": "Transport Port",
-      "description": "Elasticsearch transport port"
+      "description": "Elasticsearch transport port for node-to-node communication"
     }
   }
 }