Create extractResourceOwnerAndBucket() helper to consolidate the repeated pattern
of unmarshaling metadata and extracting bucket name from resource path. This
pattern was duplicated in handleTagResource, handleListTagsForResource, and
handleUntagResource. Update all three handlers to use the helper.
Also update remaining uses of getPrincipalFromRequest() (in handler_bucket_create,
handler_bucket_get_list_delete, handler_namespace) to use getAccountID() after
consolidating the two identical methods.
Replace misleading character-only error message with generic 'invalid bucket
name'. The isValidBucketName() function checks multiple constraints beyond
character set (length, reserved prefixes/suffixes, start/end rules), so a
specific character message is inaccurate.
Ensured bucket ownership is correctly attributed to the authenticated
account ID and updated ARNs to use the request-derived account ID. Added
standard S3 existence checks for bucket deletion.
- Implement strict table name validation (prevention of path traversal and character enforcement)
- Add nil checks for entry.Entry in all listing loops to prevent panics
- Propagate backend errors instead of swallowing them or assuming 404
- Correctly map filer_pb.ErrNotFound to appropriate S3 error codes
- Standardize existence checks across bucket, namespace, and table handlers
- Add permissions.go with permission definitions and checks
- Define permissions for all 21 S3 Tables operations
- Add permission checking helper functions
- Add getPrincipalFromRequest to extract caller identity
- Implement access control in CreateTableBucket, GetTableBucket, DeleteTableBucket
- Return 403 Forbidden for unauthorized operations
- Only bucket owner can perform operations (extensible for future policies)
- Add AuthError type for authorization failures
