docs: guide on using Rails migrations with Hasura (#1186)

[Mahi-korrapati]

Summary

This PR adds a new documentation guide explaining how to use Ruby on Rails migrations with Hasura GraphQL Engine.

The guide covers:

• Creating and running Rails migrations for PostgreSQL
• Reflecting schema changes in Hasura
• Reloading Hasura metadata
• Tracking new tables
• Integrating Rails migrations in CI/CD workflows

Motivation

This addresses issue #1186, which requested a clear guide on managing database migrations with Rails while using Hasura.

Checklist

• [x] Added new guide under v2/docs/graphql/core/guides/integrations/rails-migrations.md
• [x] Follows Hasura documentation structure and formatting
• [x] Provides practical steps and example migration code

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Please review when you have time. Thank you! 🙏