`/fleet/certificates` validation missing

[getvictor]

Fleet version:
4.79
Web browser and operating system:

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💥  Actual behavior

Missing/bad error messages for:

• when a user is adding a certificate via POST /api/v1/fleet/certificates, Fleet validates the name and returns an error if the user specifies non-supported characters, or a too-long name, or a duplicate name.

🛠️ To fix

TODO

🧑‍💻  Steps to reproduce

These steps:

• Have been confirmed to consistently lead to reproduction in multiple Fleet instances.
• Describe the workflow that led to the error, but have not yet been reproduced in multiple Fleet instances.

1. TODO
2. TODO

🕯️ More info (optional)

N/A

[getvictor]

Although marked as unreleased, adding a 1 point value since we assumed this endpoint was done for 4.78 and did not require additional work.