Develop a simplified service similar to S3

Suppose we already have a file Storage that does not store any file metadata information and provides a simple HTTP interface: POST for uploading files to the storage (returns a string identifier in response), GET for retrieving a file by this identifier, and DELETE for removing a file from Storage. When designing, focus on a basic set of functions including creating a user, creating a bucket for this user, uploading an object to the bucket under a specified key, and deleting the object.