[services] Backup - Send log - add store in database

Summary:
Depends on D3585

Add logic for storing the log data in the database.

Test Plan:

cd services
yarn run-backup-service

Reviewers: palys-swm, jimpo, varun, geekbrother

Reviewed By: palys-swm

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

Differential Revision: https://phabricator.ashoat.com/D3586