feat(crd): define Namespace spec and validation

[tomba7]

Part of #5

What was changed

• Defined NamespaceSpec for the Namespace CRD. Each field maps to its corresponding field in the Temporal Cloud namespace proto.
• Added gdt validation tests.

Why?

• Users need a typed spec to declare Temporal Cloud Namespaces before the controller can reconcile them.

Validation Trade-offs considered

1. Validate in the CRD
   • Pro: instant feedback, since kubectl apply rejects a bad manifest before anything reaches Temporal Cloud.
   • Con: Cloud-defined limits (tag rules, metadata.name format, retention range) are only documented on the Cloud docs site, not in the proto, so a CRD copy can drift stricter than Cloud and block valid configs.
2. Validate in Temporal Cloud
   • Pro: always matches Cloud's current rules, and keeps the CRD and its tests small.
   • Con: slower feedback, since errors show in the CR's status at reconcile time rather than at apply.

This PR mostly starts with option 2, with the CRD checking only structure and rules that don't depend on Cloud policy. We'll add stricter CRD checks as we test against Temporal Cloud and iterate.

Testing

• On a kind cluster with the operator deployed, make test-e2e passes.
• kubectl explain namespaces.spec --api-version=cloud.temporal.io/v1alpha1 shows each field's Cloud mapping.

[Copilot]

🔵 Needs a closer look

The broad public CRD contract and immutable CEL rules warrant final human validation against the Temporal Cloud API.

0 open findings

What changed in this PR

Defines the typed Namespace CRD specification, schema validation, examples, and end-to-end validation coverage.

Changes:

• Adds Namespace API types and generated CRD/deep-copy artifacts.
• Adds structural, enum, uniqueness, capacity, and update validation.
• Documents and tests valid and invalid Namespace manifests.

File	Description
api/​cloud/​v1alpha1/​namespace.go	Defines Namespace specification types and validation markers.
api/​cloud/​v1alpha1/​zz_generated.deepcopy.go	Adds generated deep-copy support.
deploy/​kustomize/​crd/​bases/​cloud.temporal.io_namespaces.yaml	Publishes the generated CRD schema.
examples/​namespace.yaml	Provides an example Namespace manifest.
README.md	Documents creation and validation.
test/​e2e/​namespace/​validation.yaml	Tests CRD validation behavior.
test/​e2e/​namespace/​testdata/​minimal.yaml	Supplies the minimal valid fixture.
test/​e2e/​namespace/​happy-default.yaml	Updates the lifecycle test for required fields.
.mk/​test.mk	Adds the validation test target.
.mk/​gen.mk	Enables generated CRD descriptions.
.gitignore	Ignores IDE metadata.

Files not reviewed (1)

• api/cloud/v1alpha1/zz_generated.deepcopy.go: Generated file

🧠 Review effort: Balanced

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