[BUG] build fails on main due to missing OpenSearchIntegTestCase#createRestClient

[rursprung]

What is the bug?

the build fails:

$ ./gradlew build
[..]
> Task :compileTestJava
....\src\test\java\org\opensearch\path\to\plugin\RenamePluginIT.java:35: error: cannot find symbol
        Response response = createRestClient().performRequest(new Request("GET", "/_cat/plugins"));
                            ^
  symbol:   method createRestClient()
  location: class RenamePluginIT
Note: ....\src\test\java\org\opensearch\path\to\plugin\RenamePluginIT.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
1 error

How can one reproduce the bug?

try to build the project: ./gradlew build

What is the expected behavior?

the build works

What is your host/environment?

should be unrelated to my env., but: win 11, jdk 21

Do you have any screenshots?

n/a

Do you have any additional context?

i presume that OpenSearchIntegTestCase#createRestClient has been recently removed in OpenSearch. the problem is that the plugin (template) pulls in the snapshot of an upcoming major release, so the API is not yet stabilised and can break regularly.