feat(reindex): add EXPORT-based merge ingestion for reindex using file-ready Kafka events and S3-backed record files

[psmagin]

Purpose

Implement reindex EXPORT flow support and complete related refactoring/documentation updates for mod-search reindex processing.

This change is needed to support file-based merge ingestion (inventory.reindex.file-ready) in addition to publish-based ingestion, and to document/configure the new runtime knobs.

Approach

• Added EXPORT-mode processing path for merge ingestion:
  • Consume ReindexFileReadyEvent
  • Read exported records from S3-compatible storage
  • Persist records to intermediate tables in batches
• Added trace_id support in merge ranges (merge_range.trace_id) and wired it into export request payloads.
• Introduced remote storage configuration/bean binding gated by folio.reindex.reindex-type=EXPORT.
• Added Kafka listener/container config for file-ready events and refactored reindex Kafka container-factory duplication.
• Refactored orchestration code to reduce duplication in merge success/failure handling and batch save logic.
• Updated diagrams and feature docs for full/upload flow, including PUBLISH vs EXPORT branch.
• Updated module descriptor + README environment variable documentation.

Changes Checklist

• API Changes: No new public REST paths; existing reindex APIs unchanged.
• Database Schema Changes: Added trace_id column to merge_range via Liquibase (changes/v6.0/add-trace-id-range-column.xml).
• Interface Version Changes: None.
• Interface Dependencies: Added org.folio:folio-s3-client dependency.
• Permissions: No permission changes.
• Logging: Added/updated logs for new reindex event paths and storage initialization.
• Unit Testing: Updated/ran reindex orchestration unit tests.
• Integration Testing: Existing integration tests updated in codebase; full suite not run in this update session.
• Manual Testing: Not performed in this update session.
• NEWS: Not updated in this PR.

Related Issues

MSEARCH-1175

Learning and Resources (if applicable)

• FOLIO RFC-0003 Breaking Changes guidance was used to assess impact classification.

Screenshots (if applicable)

N/A

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
88.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud