[Identity] Add opaque2 users table

Summary:
Add users table for opaque2 identity users.

https://linear.app/comm/issue/ENG-3558

Test Plan:

nix develop
comm-dev services start

cd services/terraform
./run.sh
# creates identity-users-opaque2 table

Reviewers: varun, bartek, ashoat

Reviewed By: varun

Subscribers: tomek, atul

Differential Revision: https://phab.comm.dev/D7241