opensearchutil: add missing bulk indexer response item fields

[igungor]

Description

If a bulk request contains any script error, Opensearch server points to
what is wrong with the request. This information is valuable to those
debug what is going on under the hood.

This PR adds missing bulk indexer response item fields.

Reproducer script

#!/bin/bash

INDEX="test"
OSURL="http://localhost:9200"


curl -X POST "$OSURL/$INDEX/_bulk?pretty&refresh=true" -H 'Content-Type: application/json' -d '
{"update":{"_id":"1","_index":"test"}}
{"script":{"source":"ctx._source.x = params.x","params":{"x":2}},"upsert":{"x":"1"}}
'

# null pointer exception: ctx._source.y 
curl -X POST "$OSURL/$INDEX/_bulk?pretty&refresh=true" -H 'Content-Type: application/json' -d '
{"update":{"_id":"1","_index":"test"}}
{"script":{"source":"if (ctx._source.y < params.x) {ctx._source.y = params.x}","params":{"x": 2}},"upsert":{"x":"1"}}
'

Opensearch response

{
  "took" : 287,
  "errors" : false,
  "items" : [
    {
      "update" : {
        "_index" : "test",
        "_type" : "_doc",
        "_id" : "1",
        "_version" : 1,
        "result" : "created",
        "forced_refresh" : true,
        "_shards" : {
          "total" : 2,
          "successful" : 2,
          "failed" : 0
        },
        "_seq_no" : 0,
        "_primary_term" : 1,
        "status" : 201
      }
    }
  ]
}
{
  "took" : 3,
  "errors" : true,
  "items" : [
    {
      "update" : {
        "_index" : "test",
        "_type" : "_doc",
        "_id" : "1",
        "status" : 400,
        "error" : {
          "type" : "illegal_argument_exception",
          "reason" : "failed to execute script",
          "caused_by" : {
            "type" : "script_exception",
            "reason" : "runtime error",
            "script_stack" : [
              "if (ctx._source.y < params.x) {",
              "                          ^---- HERE"
            ],
            "script" : "if (ctx._source.y < params.x) {ctx._source.y = params.x}",
            "lang" : "painless",
            "position" : {
              "offset" : 26,
              "start" : 0,
              "end" : 31
            },
            "caused_by" : {
              "type" : "null_pointer_exception",
              "reason" : null
            }
          }
        }
      }
    }
  ]
}

Check List

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[VijayanB]

@igungor can you amend your first commit instead of empty second commit to keep this PR simple.

git commit --amend  --signoff 

[VijayanB]

Are all this fields are non-optional if error exists?

[igungor]

For the case I shared, yes they're non-optional. I'm not sure about other errors cases.

[VijayanB]

If we are not sure, we should make it optional too so that it will not break. Can you make those extra variables as pointer and add omitempty

[igungor]

Done.

[igungor]

@igungor can you amend your first commit instead of empty second commit to keep this PR simple.

git commit --amend  --signoff 

Done.

[igungor]

PTAL

DCO

[VijayanB]

Looks good. Can you merge it into one commit with sign off or amend for last commit?

[igungor]

Looks good. Can you merge it into one commit with sign off or amend for last commit?

Done.

[vamshin]

LGTM! Thanks