Model the bucket publicRead field #80

cozystack/cozystack#5252 adds an optional top-level spec.publicRead boolean to the Bucket application. The provider models cozystack_bucket with a hand-written schema, so the field is not reachable from Terraform until it is added there.

What changes upstream

• New field: publicRead (bool, default false). When true, the bucket's objects are served to anyone without credentials at <endpoint>/<bucket>/<key>; anonymous callers cannot list the bucket or write to it.
• Only the bucket kind gets it.

Suggested change

In internal/provider/bucket_resource.go, bucket_data_source.go and bucket_model.go: the attribute in the schema, the model field, and the expand/flatten pair, plus docs/resources/bucket.md and docs/data-sources/bucket.md.

locking is the closest existing attribute and has the same default (false), so flatten can read an absent publicRead as false. Expand should send publicRead only when it is set, rather than restating the default, so a provider used against a Cozystack release that predates the field keeps working.

This only applies once cozystack/cozystack#5252 is merged and the api/apps/v1alpha1 pin is bumped.