Read one barrier receipt (?wait_ms= up to 5000)

{  "barrier_id": "string",  "volume_id": "string",  "generation": 1,  "state": "pending",  "covers": {},  "attachments_at_barrier": [    {      "attachment_id": "string",      "sandbox_id": "string",      "host_id": "string",      "mount_path": "string",      "mode": "string",      "state_at_barrier": "string",      "verification": "confirmed",      "reason": "string"    }  ],  "reason": "storage_binding_unconfirmed",  "created_at": "string",  "settled_at": "string",  "poll_after_ms": 0}