[FEAT] OIDC client backend

[chris-okuda]

Scope of changes

Adds the OIDCClient store model and associated API backend. Does not include the UI for now, as the OIDC project was put on the back burner.

Fixes SC-36929

Type of change

• new feature
• bug fix
• documentation
• testing
• technical debt
• other (describe)

Acceptance criteria

I have added tests that verify the behavior, please let me know if you can see any further tests.

I used Cursor AI heavily during this project as a learning experience, and I did a thorough code review of it myself prior to submitting this PR as well as editing a ton of the code myself by hand where required. I performed step by step instructions, so that I could review this as it developed slowly, rather than all at once. I have looked at every line of this code myself after the bot got to it and edited a lot of the code. The tests are sometimes a bit messy, but from my review they do test the functionality successfully for errors.

Definition of Done

• I have manually tested the change running it locally (having rebuilt all containers) or via unit tests
• I have added unit and/or integration tests that cover my changes
• I have added new test fixtures as needed to support added tests
• I have updated the dependencies list if necessary (including updating yarn.lock and/or go.sum)
• Check this box if a reviewer can merge this pull request after approval (leave it unchecked if you want to do it yourself)
• I have notified the reviewer via Shortcut or Slack that this is ready for review
• Documented service configuration changes or created related devops stories

Reviewer(s) checklist

• Any new user-facing content that has been added for this PR has been QA'ed to ensure correct grammar, spelling, and understandability.
• Are there any TODOs in this PR that should be turned into stories?

[daniellemaxwell]

The work completed here to set up the OIDC client is thorough and the tests look good. I added a comment about potentially consolidating the Validate methods and one about the oidcclient tests.