feat(crd): Stabilise Entra backend (#801)

* feat(crd): Stabilise Entra backend

* chore(crd): Update versions in code

* feat: Add conversion webhook server

* feat(helm): Adjust templates for CRD versioning/conversion

* docs: Mark Entra backend as non-experimental

* chore: Add changelog entry

* docs: Bump OpaClusters to v1alpha2

Author: Techassi

CHANGELOG.md

@@ -14,6 +14,7 @@ All notable changes to this project will be documented in this file.
 
 ### Changed
 
+- Introduce `v1alpha2` OpaCluster and mark UIF Entra backend as non-experimental ([#801]).
 - Deprecate OPA 1.8.0 ([#797]).
 - user-info-fetcher: Move backend initialization and credential resolution into backend-specific implementations ([#782]).
 
@@ -31,6 +32,7 @@ All notable changes to this project will be documented in this file.
 [#795]: https://github.com/stackabletech/opa-operator/pull/795
 [#797]: https://github.com/stackabletech/opa-operator/pull/797
 [#799]: https://github.com/stackabletech/opa-operator/pull/799
+[#801]: https://github.com/stackabletech/opa-operator/pull/801
 
 ## [25.11.0] - 2025-11-07