[identity] Add function to check if user has backup

Summary:
Address ENG-9692.
We call the backup info endpoint to see if user has backup

Generally I think this is not perfect and we could create a dedicated backup service endpoint for this which would query directly by user_id and be callable only by other services

Test Plan: Tested in the next diff

Reviewers: kamil, varun

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D14072