[Jordan Olshevski (jveski)]

Removes the implicit racer-object default ClusterCache name. Pods that opt in to the racer-object sidecar must now set the racer.unbounded-cloud.io/object-cache annotation, and the injector webhook denies them if it is missing. racer-object also fails at startup when --cache is not set. This stops a pod from silently attaching to a cache that happens to be named racer-object. Docs are updated to match.

[Copilot]

🟢 Approval recommended

Static review found no blocking issues; validation, regression coverage, and documentation consistently enforce explicit cache selection.

No open issues 🎉

What changed in this PR

Removes the implicit racer-object ClusterCache default so workloads must explicitly select their cache, preventing accidental attachment to an unrelated cache.

Changes:

• Requires object-cache for sidecar injection and --cache for racer-object startup.
• Adds missing-cache regression cases and updates existing tests to specify a cache.
• Updates reference documentation and Azure Blob examples to show explicit cache selection.

File	Description
internal/​racer/​injector/​injector.go	Rejects missing cache annotations instead of applying a default.
internal/​racer/​injector/​injector_test.go	Covers missing-cache denial and updates pod fixtures.
docs/​content/​reference/​racer-object.md	Documents required cache selection and updates the example.
docs/​content/​guides/​azure-blob-cache.md	Adds the required cache annotation to deployment instructions.
cmd/​racer-object/​main.go	Requires an explicit, nonempty --cache value.
cmd/​racer-object/​main_test.go	Tests required cache selection and updates command arguments.
cmd/​racer-object/​azure_test.go	Supplies explicit cache arguments in provider tests.

_{Review effort: Balanced}