Provide the ability to show or hide items in the LeftBar (dashboard)

Hi,

Our current on-premise instance of Onyxia does not yet use Files (S3) feature. There is a '/my-files' shortcut on the LeftBar that leads to a dialog box indicating that S3 is not configured. It would be cool to offer the possibility of adding an entry here (https://github.com/InseeFrLab/onyxia/blob/main/web/.env) to toggle its display.

I believe this feature could be apply to both the 'My Files' and 'Data Explorer' shortcuts.

What do you think about this feature?