[identity] Store social proof in users table

Summary:
Part 1 of ENG-6480.
When wallet user is being registered, we should store the social proof in the users table.

Depends on D10762

Test Plan: Called LogInWalletUser RPC and checked (awslocal dynamodb scan) that the social proof is stored in the users table.

Reviewers: varun, michal, will

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10764