MLH-1397 write search log and audits to write cluster only (ES Isolation)

[sriram-atlan]

Change description

write search log and audits to write cluster only (ES Isolation)
Tested in staging. Staging PR #5500

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

https://atlanhq.atlassian.net/browse/MLH-1397

Fix #1

Helm Config Changes for Running Tests (Staging PR)

Does this PR require Helm config changes for testing?

• Tests are NOT required for this commit. (You can proceed with the PR.) ✅
• No, Helm config changes are not needed. (You can proceed with the PR.) ✅
• Yes, I have already updated the config-values on enpla9up36. (You can proceed with the PR.) ✅
• Yes, but I have NOT updated the config-values. (Please update them before proceeding; or, tests will run with default values.)⚠️

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable

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Note

Adds support for a separate Elasticsearch write cluster for entity audits and access-audit index creation, preferring new write-host config when present.

• Elasticsearch write isolation:
  • Introduce INDEX_WRITE_BACKEND_CONF (atlas.graph.index.search.write.hostname) and prefer it over INDEX_BACKEND_CONF when resolving ES hosts via getESHosts().
  • Update ESBasedAuditRepository to use write hosts for low-level ES client initialization (getHttpHosts() now uses getESHosts()).
  • Update AccessAuditLogsIndexCreator to resolve ES hosts/port from write hosts; adjust logs to reference write-host property.
• API adjustments:
  • Constructors/methods now throw AtlasException where ES host resolution is required (e.g., AccessAuditLogsIndexCreator, Atlas.initAccessAuditElasticSearch).
• Cleanup:
  • Remove unused helpers and credential-related code in AccessAuditLogsIndexCreator (e.g., getRestClientBuilder, toArray).

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