Enhanced Generator Code to generate Endpoints using OpenSearch API Specifications

[saimedhi]

Description

Enhanced Generator Code to generate Endpoints using OpenSearch API Specifications.

• Follow the steps below to run the generator:

php util/GenerateEndpoints.php   (to run the generator)
composer run php-cs            (to format)

• View the Generated Endpoints here. Subsequent PRs will address any minor adjustments needed in the generated endpoints.
• The OpenSearch API specification repository can be found here.
• The specification can be downloaded from the releases section.

Issues Resolved

Related to #97

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[saimedhi]

@shyim, @dblock, @VachaShah please take a look. Thank you.

• View the Generated Endpoints in PR 195.
• Subsequent PRs will address any minor adjustments needed in the generated endpoints.