Document a downgrade process

Hi.

After reading the documentation it is not clear for me, how the downgrade process should be performed over the database. Could you please describe somewhere in the documentation:

- How to downgrade the database to the older version (hopefully with no downtime)
- Maybe some compatibility policies and notes between versions

Thanks in advance!

No documentation file, test, or entry point is named. Research the supported database downgrade procedure, no-downtime constraints, and version-compatibility policy before documenting them. Done means the documentation clearly explains the process and compatibility considerations across versions.

Written by the indexing model from the issue text.