[DOC] Upgrading OpenSearch should also feature Migration assistant as an option

[peternied]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request.
Upgrading with a new cluster is not covered in the Upgrade OpenSearch page [1]. While different options of in-place upgrades are presented they are inherently risky since there is no way to 'un-upgrade'.

Upgrading with a new cluster is possible for OpenSearch customers with the Migration Assistant that was recently included in the documentation website link [2], this seems like a great connection to make to improve this experience for OpenSearch customers.

This will become even more relevant for customers as OpenSearch 3.0.0 is proposed [3]

Version:
All versions of OpenSearch.

What other resources are available?

• [1] Main OpenSearch upgrade page https://opensearch.org/docs/latest/install-and-configure/upgrade-opensearch/index/
• [2] Migration Assistant documentation root https://opensearch.org/docs/latest/migration-assistant/
• [3] [PROPOSAL] Release OpenSearch 3.0 .github#250

[peternied]

Thanks @andrross for prompting for the creation of this issue

FYI - @sumobrian

[Naarcha-AWS]

@peternied: Actively working on a pull request that address this. Should have a PR up that modifies the majority of upgrade pages to emphasize Migration Assistant before the end of the year.