[keyserver] add logic to update acknowledgment table

Summary:
The function should be called after detecting login from a proper source.

Functionality:

• a. if there is no record with the given user and policy it means that this is a new one - so It adds a new row
• b. if there is a record with a given user and policy but confirmed is set to 0 it means that policy was updated, so it updated confirmed and date
• c. in any other case do nothing

Test Plan:
Check if described in Summary logic works for:

1. new policy
2. updated policy
3. policy accepted by user previously

Reviewers: atul, marcin, ashoat, tomek

Reviewed By: marcin, ashoat, tomek

Subscribers: ashoat, atul, abosh

Differential Revision: https://phab.comm.dev/D5311