Key of blob of retrieved attributes.

CacheControl specifies caching attributes that services may use when serving the blob. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control

ContentDisposition specifies whether the blob content is expected to be displayed inline or as an attachment. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition

ContentEncoding specifies the encoding used for the blob's content, if any. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding

ContentLanguage specifies the language used in the blob's content, if any. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Language

ContentType is the MIME type of the blob. It will not be empty. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type

Metadata holds key/value pairs associated with the blob. Keys are guaranteed to be in lowercase, even if the backend service has case-sensitive keys (although note that Metadata written via this package will always be lowercased). If there are duplicate case-insensitive keys (e.g., "foo" and "FOO"), only one value will be kept, and it is undefined which one.

CreateTime is the time the blob was created, if available. If not available, CreateTime will be the zero time.

ModTime is the time the blob was last modified.

Size is the size of the blob's content in bytes.

MD5 is an MD5 hash of the blob contents or nil if not available.

ETag for the blob; see https://en.wikipedia.org/wiki/HTTP_ETag.