Remove references to admin:admin

DEVELOPER_GUIDE.md

@@ -137,12 +137,11 @@ Additionally, it is also possible to run a cluster with security enabled:
 ./gradlew run -Dsecurity.enabled=true
 ```
 
-By default, if `-Dsecurity.enabled=true` is passed the following defaults will be used: `https=true`, `user=admin` and
-`password=admin`.
+By default, if `-Dsecurity.enabled=true` is passed the following defaults will be used: `https=true`, `user=admin`. There is no default password and it is to be set as `password=<admin-password>`.
 
-Then, to access the cluster, we can run
+Then, to access the cluster, we can run the below command. <admin-password> parameter is the password set by admin.
 ```bash
-curl https://localhost:9200 --insecure -u admin:admin
+curl https://localhost:9200 --insecure -u admin:<admin-password>
 
 {
   "name" : "integTest-0",
@@ -191,7 +190,7 @@ Integration tests can be run with remote cluster. For that run the following com
 In case remote cluster is secured it's possible to pass username and password with the following command:
 
 ```
-./gradlew :integTestRemote -Dtests.rest.cluster=localhost:9200 -Dtests.cluster=localhost:9200 -Dtests.clustername="integTest-0" -Dhttps=true -Duser=admin -Dpassword=admin
+./gradlew :integTestRemote -Dtests.rest.cluster=localhost:9200 -Dtests.cluster=localhost:9200 -Dtests.clustername="integTest-0" -Dhttps=true -Duser=admin -Dpassword=<admin-password>
 ```
 
 ### Debugging

build.gradle

@@ -62,6 +62,7 @@ def opensearch_tmp_dir = rootProject.file('build/private/opensearch_tmp').absolu
 opensearch_tmp_dir.mkdirs()
 
 ext {
+    System.setProperty("OPENSEARCH_INITIAL_ADMIN_PASSWORD", "myStrongPassword123!")
     isSnapshot = "true" == System.getProperty("build.snapshot", "true")
     projectSubstitutions = [:]
 
@@ -85,9 +86,9 @@ ext {
         cluster.getNodes().forEach { node ->
             var creds = node.getCredentials()
             if (creds.isEmpty()) {
-                creds.add(Map.of('username', 'admin', 'password', 'admin'))
+                creds.add(Map.of('username', 'admin', 'password', System.getProperty("OPENSEARCH_INITIAL_ADMIN_PASSWORD")))
             } else {
-                creds.get(0).putAll(Map.of('username', 'admin', 'password', 'admin'))
+                creds.get(0).putAll(Map.of('username', 'admin', 'password', System.getProperty("OPENSEARCH_INITIAL_ADMIN_PASSWORD")))
             }
         }
 
@@ -302,7 +303,7 @@ integTest {
         // If security is enabled, set is_https/user/password defaults
         is_https = is_https == null ? "true" : is_https
         user = user == null ? "admin" : user
-        password = password == null ? "admin" : password
+        password = password == null ? System.getProperty("OPENSEARCH_INITIAL_ADMIN_PASSWORD") : password
     }
     systemProperty("https", is_https)
     systemProperty("user", user)