[services] Backup - Database - add Log Item

Summary:
Item for UserPersist database entity

Depends on D3082

Test Plan: -

Reviewers: palys-swm, geekbrother, varun, ashoat, jimpo

Reviewed By: palys-swm, ashoat

Subscribers: jimpo, benschac, ashoat, palys-swm, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D3084