unknown field [must_exist] for post _aliases remove action

[payalm08]

Describe the bug
When executing api post _alias with remove action with ""must_exist": true" in request, getting error unknown field [must_exist]

To Reproduce
Steps to reproduce the behavior:

POST _aliases 
{
   "actions": [
    {
      "remove": {
        "index": "testIndex",
        "aliases": "testAlias",
        "must_exist": true
      }
    }
  ]
}

Error

{
  "error" : {
    "root_cause" : [
      {
        "type" : "x_content_parse_exception",
        "reason" : "[7:9] [remove] unknown field [must_exist]"
      }
    ],
    "type" : "x_content_parse_exception",
    "reason" : "[7:23] [aliases] failed to parse field [actions]",
    "caused_by" : {
      "type" : "x_content_parse_exception",
      "reason" : "[7:23] [alias_action] failed to parse field [remove]",
      "caused_by" : {
        "type" : "x_content_parse_exception",
        "reason" : "[7:9] [remove] unknown field [must_exist]"
      }
    }
  },
  "status" : 400
}

Expected behavior
Expected response

{
  "acknowledged" : true
}

Host/Environment (please complete the following information):

• Version - OS 1.2

Reported elastic/elasticsearch#62642

[dblock]

Looks like this isn't implemented. Would gladly accept a PR implemented from scratch in OpenSearch.

[gaobinlong]

The parameter must_exist exists in the code but the functionality is not complete yet, I'm trying to fix this issue.

[gaobinlong]

I've created a PR for this issue, could anyone help to review?

[kiranprakash154]

Hi, are we on track for this to be released in 2.12 ?

[gaobinlong]

Hi, are we on track for this to be released in 2.12 ?

Yes, the bug fix will be released in 2.12.0.

[gaobinlong]

Closed by #11210.