Optional
An entity tag (ETag) is an opaque identifier assigned by a web server to a specific version of a resource found at a URL.
Key of the object
Creation date of the object.
The user-defined metadata for the object uploaded to S3.
https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingMetadata.html#UserMetadata
Size of the body in bytes.
An entity tag (ETag) is an opaque identifier assigned by a web server to a specific version of a resource found at a URL.