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

• [x] Product feature
• [x] Bug fix
• [ ] Performance improvement
• [ ] Refactor
• [ ] Other

Tested Environments

• [ ] Development
• [ ] Staging
• [ ] Production

Before Requesting Review

• [x] 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?
• [x] Is there a clear title that explains what the PR does?
• [x] Have you used intuitive function, variable and other naming?
• [ ] Have you requested security and/or privacy review if needed
• [x] Have you performed a self review of this PR?

Manual Test Plan

[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.