[services] helper to update the users table

Summary:
we're going to use this aws rust sdk method a lot, so we should move some of this logic to a helper function

Depends on D4559

Test Plan: will be tested in the subsequent diffs that use the helper

Reviewers: palys-swm, karol-bisztyga

Reviewed By: palys-swm, karol-bisztyga

Subscribers: ashoat, Adrian, atul, yayabosh

Differential Revision: https://phab.comm.dev/D4562