[BUG] _render Operation is not working in OS_2.11

[niravpi]

What is the bug?
OpenSearch provide support for _render operation which helps to validate stored template, attached reference documents below.

• OpenSearch Doc : https://opensearch.org/docs/latest/api-reference/search-template/#save-and-execute-search-templates

But for OS_2.11 FGAC enabled domains _render operation is not working as it is failing with the following exception

    {
        "type": "security_exception",
        "reason": "Unexpected exception indices:data/read/search/template"
      }

While analyzing further observed that the issue might be related to recent PR

• Make SearchTemplateRequest implement IndicesRequest.Replaceable OpenSearch#9122

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Create FGAC enabled OS_2.11 domain
2. Then perform the following operations on the domain
3. First save search template as a script

POST _scripts/play_search_template
{
  "script": {
    "lang": "mustache",
    "source": {
      "from": "{{from}}{{^from}}0{{/from}}",
      "size": "{{size}}{{^size}}10{{/size}}",
      "query": {
        "match": {
          "play_name": ""
        }
      }
    },
    "params": {
      "play_name": "Henry IV"
    }
  }
}

4.Then try to perform render operation to validate saved template

POST _render/template
{
  "id": "play_search_template",
  "params": {
    "play_name": "Henry IV"
  }
}

5. See error as below

{
  "error": {
    "root_cause": [
      {
        "type": "security_exception",
        "reason": "Unexpected exception indices:data/read/search/template"
      }
    ],
    "type": "security_exception",
    "reason": "Unexpected exception indices:data/read/search/template"
  },
  "status": 500
}

What is the expected behavior?
render operation should have worked and the output for the above reproduction steps should be as follow instead of exception

{
  "template_output": {
    "from": "0",
    "size": "10",
    "query": {
      "match": {
        "play_name": "Henry IV"
      }
    }
  }
}

What is your host/environment?

• OpenSearch version OS_2.11

Do you have any screenshots?

[expani]

Thanks @niravpi for reporting the issue.
I believe it's already being tracked at #3672

[cwperks]

Closing as duplicate of #3672