About file storage

[cndingwei]

Now, regardless of whether the files synchronized to the server already exist on the server, they will be uploaded again, even if they are different folders for the same user.
Suggestions:

1. All files uploaded by all users are uploaded to the same location. When uploading files, if the same files exist on the server, they will not be uploaded again.
2. The files uploaded by users are presented to users through the "association" relationship.
3. If the user modifies the file, it will appear in the form of "version" management. The "version" file only has access rights to the user, unless the user shares the file with other users.
4. When the user shares the file with other users, the "association" relationship is also added to the real file. If the user wants to delete the file, the user will be asked whether the file has been shared with a certain user and whether to keep the sharing. If "keep", the user's access rights will be revoked.