added type check for pipeline aggregator types in Transform initializ…

[n-dohrmann]

…ation

Issue #, if available:
#671

Description of changes:
Error being fixed: the init block of Transform.kt did not check for pipeline type aggregator factories, which meant it was possible for unsupported aggregation types to be passed in for a transform job without raising an exception.

Changes made: Added a new require statement that checks aggregations.pipelineAggregatorFactories for unsupported types.

CheckList:

• [ x] Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

Merging #1014 (6a37e2b) into main (d42cc69) will decrease coverage by 0.09%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##               main    #1014      +/-   ##
============================================
- Coverage     74.75%   74.66%   -0.09%     
+ Complexity     2789     2787       -2     
============================================
  Files           366      366              
  Lines         16358    16360       +2     
  Branches       2336     2337       +1     
============================================
- Hits          12228    12216      -12     
- Misses         2830     2848      +18     
+ Partials       1300     1296       -4     

Files	Coverage Δ
...earch/indexmanagement/transform/model/Transform.kt	85.29% <50.00%> (-0.30%)	⬇️

... and 6 files with indirect coverage changes

[bowenlan-amzn]

@n-dohrmann follow up task on this: add a unit test case for this scenario

[bowenlan-amzn]

Also include your reproduce steps and result in this PR

[n-dohrmann]

Reproduce steps:
1.) Launch OpenSearch index-management cluster and dashboards, load in sample flight data
2.) Run the following requests in DevTools:

PUT /_cluster/settings
{
  "persistent": {
    "logger.org.elasticsearch.discovery": "DEBUG"
  }
}

PUT _plugins/_transform/bucket_script_test
{
  "transform": {
    "enabled": true,
    "continuous": true,
    "schedule": {
      "interval": {
        "period": 1,
        "unit": "Minutes"
      }
    },
    "description": "Sample transform job ",
    "source_index": "opensearch_dashboards_sample_data_flights",
    "target_index": "transform_test_target",
    "data_selection_query": {
      "match_all": {}
    },
    "page_size": 1,
    "groups": [
      {
        "terms": {
          "source_field": "AvgTicketPrice",
          "target_field": "original_price"
        }
      },
      {
        "terms": {
          "source_field": "DistanceKilometers",
          "target_field": "discount"
        }
      }
    ],
    "aggregations": {
       "final_price": {
        "bucket_script": {
            "buckets_path": {
                "p": "price",
                "d": "discount"
            },
            "script": "params.p * (1 - params.d)"
        }
    }
    }
  }
}

3. ) The following (expected) error message is received: