Ethereum-Based Decentralized File Storage System

This is a Solidity smart contract called "Box" that implements a file storage system. The contract allows for adding files to the storage system, checking storage capacity, managing allowed users, and requesting access to the system. The contract is owned by a single owner, who can manage the system, add and remove allowed users, and accept requests for access. The contract uses several data structures, including structs and mappings, to keep track of files, allowed users, and requests for access, and it includes a modifier that restricts access to certain functions to the contract owner only.