Refactor Migrations and Upgrades Documentation

[Naarcha-AWS]

Description

This PR represents a comprehensive restructuring of OpenSearch's migration and upgrade documentation, transforming scattered content into a cohesive, user-centric resource. This refactoring transforms upgrade and migration documentation into a cohesive, user-centered resource that guides users through the complete migration journey from initial assessment to successful completion for Migration Assistant, and identifies other available options.

Key Changes Made

1. Major Directory Restructuring

• __Moved content to _migrate-or-upgrade/ and various upgrade and migration options discoverable from this location.
• Consolidated migration documentation under a unified structure
• Updated navigation hierarchy to reflect new organization

2. Content Architecture Improvements

• Migration Journey Enhancement: Added structured migration phases with clear step-by-step guidance
• Requirements Clarification: Updated migration and upgrade requirements and technical prerequisites
• Migration Phases: Added comprehensive migration workflow with distinct phases

3. Navigation and User Experience Enhancements

• Fixed broken links throughout the documentation
• Updated breadcrumbs and TOC structure for better navigation
• Made title casing consistent across all sections
• Improved cross-references between related topics
• Added comprehensive redirects to maintain backward compatibility

4. Configuration and Infrastructure Updates

• Added Migration Assistant section to _config.yml
• Updated home page cards to properly link to migration content
• Fixed collection permalinks and navigation structure
• Updated section names for consistency ("Migration Assistant for OpenSearch")

Strategy Behind This PR

1. Information Architecture Optimization

Problem: Migration information was fragmented across multiple sections, making it difficult for users to find comprehensive guidance.

Solution: Consolidated all migration-related content under a logical hierarchy that follows the user journey from assessment to completion.

Impact: Users can now find all migration information in one place with clear progression paths.

2. User Journey Enhancement

Problem: Users struggled to understand the complete migration process and often got lost in scattered documentation.

Solution: Created structured migration phases with clear step-by-step guidance and logical progression.

Impact: Reduced user confusion and improved migration success rates through better guidance.

3. Maintenance and Scalability

Problem: Scattered content was difficult to maintain, update, and keep consistent.

Solution: Centralized structure with consistent naming conventions and organization patterns.

Impact: Easier maintenance, updates, and future expansion of migration documentation.

4. Backward Compatibility

Problem: Major restructuring could break existing links and user bookmarks.

Solution: Comprehensive redirect strategy to maintain link integrity across the transition.

Impact: Seamless experience for existing users and preserved external references.

Version

all

Frontend features

N/A

Checklist

• By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and subject to the Developers Certificate of Origin.
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