Runtime field script params

[alejokf]

Issue

resolves https://github.com/sudo-suhas/elastic-builder/issues/201

Goal

Add support for Elasticsearch lang and params fields in runtime_mappings' script

Usage

This Typescript code:

const params = {
   factor: 2
}
const field = esb.runtimeField("long", "emit(doc['measure'].value * params.factor);")
  .lang('painless')
  .params(params)
const reqBody = esb.requestBodySearch();
reqBody.runtimeMapping('measure', field);

Will generate this query:

{
  "runtime_mappings": {
    "measure": {
      "type": "long",
      "script": {
        "lang": "painless",
        "source": "emit(doc['measure'].value * params.factor);",
        "params": {
          "factor": 2
        }
      }
    }
  }
}

Changes in PR

• Add lang field to RuntimeField
• Add params field to RuntimeField
• Add unit tests
• Make RuntimeField return this to allow calls being chained and to make the it consistent with the rest of the API, as suggested on this comment.

[sudo-suhas]

@alejokf could you please resolve conflicts add tests to ensure 100% coverage? We need tests for the following:

• https://coveralls.io/jobs/141689187/source_files/25277366975#L82
• https://coveralls.io/jobs/141689187/source_files/25277366975#L95

[alejokf]

@sudo-suhas conflicts are now fixed and coverage should be 100%