Improve experience for missing restore method

[BacLuc]

Summary

As user
I want a descriptive error message when i forget to specify the restore method
So that i can find my mistake quickly

Currently, the error message is:

2026-04-27T09:32:05Z    ERROR    k8up.operator    Reconciler error    {"controller": "restore.k8up.io", "controllerGroup": "k8up.io", "controllerKind": "Restore", "Restore": {"name":"restore-
test","namespace":"vshn-grafana"}, "namespace": "vshn-grafana", "name": "restore-test", "reconcileID": "ddccfbc2-8a88-4bb1-b1c7-6a38c3392f9e", "error": "panic: runtime error: invalid memory a
ddress or nil pointer dereference [recovered]"}

in the controller logs.

Ferrari solution: Admission hook does not permit to apply the invalid manifest.

Context

I had to ask a k8up expert to find the bug.

Out of Scope

No response

Further links

No response

Acceptance Criteria

No response

Implementation Ideas

No response