Block delete_bucket requests by an OBC account

[dannyzaken]

Explain the changes

1. Prevent the deletion of an OBC bucket by the OBC account.
2. A regular account can delete an OBC bucket according to the access policy or via RPC

Issues: Fixed #xxx / Gap #xxx

1. https://bugzilla.redhat.com/show_bug.cgi?id=2301657

Testing Instructions:

1. Create an OBC bucket
2. use the credentials associated with the OBC (in the OBC secret) and attempt to delete the bucket via s3 API (e.g. aws-cli)
3. The expected status is AccessDenied
4. Attempt to delete the bucket using the admin credentials. deletion should work.
5. Deletion of the OBC should also work and delete the underlying bucket

• Doc added/updated
• Tests added

[tangledbytes]

Maybe we can add a small test in unit_tests/test_s3_ops to ensure no regression in future.

[jackyalbo]

please move line 233 close to the check in line 245. I mean, put your code block before or after this check, not in the middle. also, I would move the @todo before the const, just as a side note...