directive to specify caching behavior of object data. If omitted and object is accessible to all anonymous users, the default will be public, max-age=3600
*`content_disposition` - (Optional) [Content-Disposition](https://tools.ietf.org/html/rfc6266) of the object data.
*`content_encoding` - (Optional) [Content-Encoding](https://tools.ietf.org/html/rfc7231#section-3.1.2.2) of the object data.
*`content_language` - (Optional) [Content-Language](https://tools.ietf.org/html/rfc7231#section-3.1.3.2) of the object data.
*`content_type` - (Optional) [Content-Type](https://tools.ietf.org/html/rfc7231#section-3.1.1.5) of the object data. Defaults to "application/octet-stream" or "text/plain; charset=utf-8".
*`storage_class` - (Optional) The [StorageClass](https://cloud.google.com/storage/docs/storage-classes) of the new bucket object.
Supported values include: `MULTI_REGIONAL`, `REGIONAL`, `NEARLINE`, `COLDLINE`. If not provided, this defaults to the bucket's default
storage class or to a [standard](https://cloud.google.com/storage/docs/storage-classes#standard) class.