fix#13938fix#14683fix#14532
#### PR Dependency Tree
* **PR #14686** 👈
This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Flexible OIDC claim mapping for email/name, automatic OIDC discovery
retry with exponential backoff, and explicit OAuth flow modes (popup vs
redirect) propagated through the auth flow.
* **Bug Fixes**
* Stricter OIDC email validation, clearer error messages listing
attempted claim candidates, and improved callback redirect handling for
various flow scenarios.
* **Tests**
* Added unit tests covering OIDC behaviors, backoff scheduler/promise
utilities, and frontend OAuth flow parsing/redirect logic.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->