Storage Metadata API: add/update not working with local file storage (Pairtree)

[zydio]

If OFS is configured with Pairtree to use a local file storage, all POST requests to add/update metadata ( /api/storage/metadata/{label} ) will fail.

This is due to the use of ​BotoOFS specific private methods in ​StorageAPIController.set_metadata(), eg: self.ofs._require_bucket(bucket), self.ofs._get_key(b, label), self.ofs._update_key_metadata(k, metadata) ... those methods can't be found in ​POTFS and this causes errors. The API should use only ​OFSInterface methods, or should conditionally make calls based off the actual type of self.ofs.

PS: I did set "ckan" as "Component" in the ticket because storage has been integrated back into the core in CKAN 1.6