[Boost] Document DataSync

**Note:** this is an important maintainability tidy-up, but is not a blocker to a React release.

@pyronaur please add details here. Migrated from trello.

Start by locating DataSync within Boost and checking for existing documentation. The issue gives no target file, required details, or validation steps; clarify those with the maintainers before starting. Done means the requested DataSync details are documented in the agreed location.

Written by the indexing model from the issue text.