Support adopting existing radosgw buckets and users

The operator previously assumed it created every user and bucket it managed:
reconciling an existing resource could overwrite its user attributes or wipe its
bucket policy, and deleting a CRD always deleted the underlying RGW object (only
Bucket had retainOnDelete). That made taking over pre-existing radosgw state
unsafe. Make adoption first-class.

- add retainOnDelete to ObjectStoreUser and BucketAccess (dedicated users), so
  deleting the CRD orphans the RGW user instead of deleting it (symmetric with
  Bucket)
- merge bucket policy instead of replacing it: the operator marks its own
  statements with a cephrgwop* Sid and preserves any statement it does not own,
  so adopting a bucket with a hand-written policy keeps it; add Bucket
  managePolicy (default true) to opt out of policy management entirely
- only reconcile user attributes the spec sets: DisplayName when non-empty and
  Suspended is now an optional *bool, so adopting a user does not reset them
- record adoption: ObjectStoreUser/Bucket status.adopted (+ printcolumn) is true
  when the RGW object already existed on first reconcile
- add GetBucketPolicy + MergeBucketPolicy; keyed adoption detection off the
  status identity field so a Pending owner wait does not mislabel it
- regenerate CRDs/deepcopy; add docs/adoption.md and
  config/samples/05-adoption.yaml; cover the merge in policy_test.go

Claude-Session: https://claude.ai/code/session_016CEncETbf8cvy1PhsHfFHM

README.md

@@ -60,6 +60,17 @@ refine it (see `config/samples/04-access-fine-grained.yaml`):
 RGW honours S3 bucket policy on **Reef 18.2+ / Squid**; condition-key support is
 a subset of AWS, so validate exotic conditions against your cluster.
 
+### Adopting existing buckets and users
+
+The operator can take over buckets/users that already exist in radosgw and hand
+them back without deleting them. In short: matching CRDs manage the resource in
+place (no recreation, keys reused, `status.adopted: true`), the bucket policy is
+**merged** so an existing hand-written policy is preserved (`spec.managePolicy:
+false` opts out entirely), and `spec.retainOnDelete` on `ObjectStoreUser` /
+`Bucket` / `BucketAccess` orphans the RGW object instead of deleting it. See
+**[docs/adoption.md](docs/adoption.md)** and
+`config/samples/05-adoption.yaml`.
+
 The `Bucket` controller renders the policy as the **union of every ready
 `BucketAccess`** that targets it, so the result is convergent regardless of the
 order objects are created or deleted. It watches `BucketAccess` and