Document Elasticsearch v9 support and v7.17 deprecation

[lieut-data]

Summary

• Add Elasticsearch v9 as a supported search backend starting from Mattermost v11.7
• Document that Elasticsearch v7.17 is no longer supported as of v11.7
• Update version references and links across setup and requirements documentation

Test plan

• Verify RST renders correctly, especially the new v9 tab and v8 note directive
• Confirm all Elastic documentation links resolve correctly

[github-actions]

Newest code from mattermost has been published to preview environment for Git SHA d71578b

[github-actions]

Newest code from mattermost has been published to preview environment for Git SHA 9ecfc75

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request updates Elasticsearch version support documentation across multiple guides. The changes reflect support for Elasticsearch v9 as the current version, deprecate v7.17 support starting with Mattermost v11.7, and update version references throughout the administration and deployment documentation.

Changes

Cohort / File(s)	Summary
Elasticsearch Version Support Updates source/administration-guide/scale/elasticsearch-setup.rst, source/administration-guide/scale/enterprise-search.rst, source/deployment-guide/software-hardware-requirements.rst	Updated Elasticsearch version references to v9 (current) and v8.19; added Elasticsearch v9 support documentation; deprecated Elasticsearch v7.17 support as of Mattermost v11.7; clarified version-agnostic directives for destructive action settings; updated AWS managed service guidance to reflect v8 and v9 client compatibility constraints.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly summarizes the main changes: documenting Elasticsearch v9 support and v7.17 deprecation, which aligns with the core objectives and file modifications across all three documentation files.
Description check	✅ Passed	The description is clearly related to the changeset, providing specific details about adding v9 support, documenting v7.17 deprecation, and updating version references—all of which match the actual file modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch support-elasticsearch-v9

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@source/administration-guide/scale/elasticsearch-setup.rst`:
- Line 46: Update the sentence that advises setting
action.destructive_requires_name to false in elasticsearch.yml to include an
explicit safety note: warn that this setting defaults to true in ES 8/9 and
disabling it permits dangerous wildcard deletes (e.g., DELETE * or DELETE .*)
that can remove system indices used for authentication; state when this
temporary change is required (only for the specific maintenance step described),
require restoring action.destructive_requires_name to true immediately after the
operation, and suggest the safer wildcard exclusion pattern "*,-.*" (exclude
system indices) as an alternative to turning the protection off.

In `@source/deployment-guide/software-hardware-requirements.rst`:
- Line 235: Update the sentence that currently reads "Elasticsearch v8.x and
v9.x are supported, and Elasticsearch v9.x or AWS OpenSearch is recommended" to
qualify v9 support by adding that Elasticsearch v9.x is supported beginning with
Mattermost v11.7 (e.g., "Elasticsearch v8.x is supported; Elasticsearch v9.x is
supported beginning with Mattermost v11.7, and Elasticsearch v9.x or AWS
OpenSearch is recommended"). Keep the existing :doc:`Learn more
</administration-guide/scale/enterprise-search>` link and adjust punctuation as
needed so the sentence remains grammatically correct.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: bb6b22b8-9355-48f2-9a3a-15003c1c0e3e

📥 Commits

Reviewing files that changed from the base of the PR and between 997af1e and 9ecfc75.

📒 Files selected for processing (3)

• source/administration-guide/scale/elasticsearch-setup.rst
• source/administration-guide/scale/enterprise-search.rst
• source/deployment-guide/software-hardware-requirements.rst

[esethna]

Adding the do not merge label so this can be rebased to the 11.7 branch when it's cut

[agarciamontoro]

Neat, thank you!