Database Schema for a file storage System

I need to build a file storage system based in users with permissions (like a Dropbox)

Additional constraints:

• the file content will be stored in AWS S3 Bucket (every user will use a specific folder created for that user only)

• a user can contain multiple files or folders

• each folder can contain multiple files or other folders (like a
  normal file system)

• a user can rename or relocate any of his own files

• a file can be shared temporarily with a link (that expires after 1
  hour or some predefined time)

• it should be secure

What is the best way yo create a relationship between them?

this is my current design:

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