Batched background migration documentation for multiple databases and restrict_gitlab_migration
Extracted from !84764 (comment 910045400) . We will need to ensure our batched background migrations documentation explain the usage of restrict_gitlab_migration
and how to choose the correct schema to use for the batched background migrations.
This documentation has been partly written in !85345 (comment 919139045) but there will need to be more updates to the batched background migration docs to refer to 2.0
and we may want to crosslink these 2 pages somehow depending on where is best to explain the restricted schema.
Edited by Dylan Griffith