<!-- Add the related story/sub-task/bug number, like Resolves#123, or
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**Related issue:** Resolves#38549
Associated documentation update PR:
https://github.com/fleetdm/fleet/pull/38702
# Checklist for submitter
- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
- [x] Input data is properly validated, `SELECT *` is avoided, SQL
injection is prevented (using placeholders for values in statements)
## Testing
- [x] Added/updated automated tests
- [x] QA'd all new/changed functionality manually
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Introduced conditional_access.cert_serial_format to choose certificate
serial number format (hex or decimal); hex is default.
* SSO certificate serial parsing now respects the configured format.
* **Bug Fixes**
* Improved parsing and error handling for certificate serial numbers
across formats.
* **Tests**
* Added unit tests for configuration validation and serial-number
parsing for both hex and decimal.
<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Victor Lyuboslavsky
063c16cffd