Implement File Updating Function

[emmalgs]

What it is

Implement a function in the FileSystemService to update user data in an existing file using the FileSystem module.

Context

Updating user data files is required when performing user data updates.

Acceptance Criteria

• A function named updateFile is defined in the FileSystemService module.
• The function accepts a user ID and updated user data as parameters.
  *The function reads the existing JSON file (based on the user ID) using fs.readFile.
• The function updates the necessary fields with the provided data.
• The function writes the updated data back to the JSON file using fs.writeFile.