Summary

Revamp of the onboarding experience aimed at providing POCs with a clearer / better structured path through the docs.

• Complete restructure of the Cloud section with a simpler, more intuitive organisation structure
• Migration guide additions (Redshift, Snowflake)
• New sections for use case overviews, comparison between OSS and Cloud products
• Improvements to formatting of guides with steps (using the vertical stepper)

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/integrations/index.mdx