feat: change request_id to disallow null and update index

[pavelbrm]

Summary

This PR updates the time_limited_v2_order_creds_unique constraint on the time_limited_v2_order_creds table, thus allowing credentials for multiple unique batches within the same period, which is necessary for Multi Device Refresh.

Type of Change

• Product feature
• Bug fix
• Performance improvement
• Refactor
• Other

Tested Environments

• Development
• Staging
• Production

Before Requesting Review

• Does your code build cleanly without any errors or warnings?
• Have you used auto closing keywords?
• Have you added tests for new functionality?
• Have validated query efficiency for new database queries?
• Have documented new functionality in README or in comments?
• Have you squashed all intermediate commits?
• Is there a clear title that explains what the PR does?
• Have you used intuitive function, variable and other naming?
• Have you requested security and/or privacy review if needed
• Have you performed a self review of this PR?

Manual Test Plan

[pavelbrm]

At the moment of writing, there have been no rows with request_id NULL in the table (both Staging and Production).

[kdenhartog]

LGTM

[evq]

lgtm! there is a race that this PR in isolation would expose us to - however the plan as I understand it is to deploy this alongside #2522 where it is fixed

[pavelbrm]

lgtm! there is a race that this PR in isolation would expose us to - however the plan as I understand it is to deploy this alongside #2522 where it is fixed

Yes, this and #2522, as well as other related PRs are all planned to go in one release, therefore the risk of the race is minimal if not zero.