[SPARK-27972] Move SQL migration guide to the top level

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 3.0.0
• Component/s: Documentation
• Assignee: Unassigned
• Reporter: Xiao Li
• Created: 07/Jun/19 01:55
• Updated: 16/Sep/19 05:08
• Resolved: 16/Sep/19 05:08

Description

Currently, only SQL and MLLib  have the dedicated section for documenting behavior changes and breaking changes. We found these guides simplify the upgrade experience for end users. 

https://spark.apache.org/docs/latest/sql-migration-guide.html

https://spark.apache.org/docs/2.4.3/ml-guide.html#migration-guide

The other components can do similar things in the same doc. Here, we propose to combine the migration guides and move it to the top level. All the components can document their behavior changes in the same PR that introduced the changes. 

Issue Links

• duplicates: SPARK-29052 Create a Migration Guide tap in Spark documentation