Provider 2.x support

[prudhvigodithi]

Description

• Provider 2.x support, coming from https://github.com/opensearch-project/terraform-provider-opensearch/pull/41, https://github.com/opensearch-project/terraform-provider-opensearch/pull/16 (thanks to @serge-r)

• This should start with provider 2.0 release that can support 2.x version of OpenSearch.

• The idea of this PR is to streamline the provider OpenSearch 2.x support.

• Removed configuring the destinations due to this bug https://github.com/opensearch-project/alerting/issues/1078. The new logic should be added to use notifications. Related issue to add the notification support https://github.com/opensearch-project/terraform-provider-opensearch/issues/30.

• Updated the repo README to add details about building and testing the provider.

• Updated the repo README with supported OpenSearch and OpenSearch Dashboards API coverage.

Issues Resolved

Part of: https://github.com/opensearch-project/terraform-provider-opensearch/issues/39

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[prudhvigodithi]

Hey @phillbaker and @serge-r can you please take a look and see how I can fix the tests ? Thank you

[prudhvigodithi]

Hey @phillbaker, @serge-r I have fixed the tests and logic that should support the 2.x version, Please review once merged this should be good start to move forward with 2.x support. Thank you

Pending: To run the tfplugindocs cli.

[prudhvigodithi]

Updated the example resource docs and the repo README file. Please check. Thanks

[prudhvigodithi]

Can we please move forward with this PR? Adding @peterzhuamazon @phillbaker @jackson-theisen @serge-r @9rnt @atammy-narmi @bbarani Thank you

[andrejvanderzee]

@phillbaker @jackson-theisen @peterzhuamazon Can you plz take this a step forward and review? Without 2.x support, this provider has not much time left to be relevant.

[peterzhuamazon]

Need review from @phillbaker @jackson-theisen as well.

Thanks.

[prudhvigodithi]

Thanks @peterzhuamazon and @andrejvanderzee. I have start with the v2.0.0-beta.1, this should be a good starting point to roll out the provider 2.x support and streamline the repo for upcoming contributions and releases.