App defined share permission flags

Moved over from since this recently came up again with ONLYOFFICE. There are several use-cases where apps like Collabora or OnlyOffice could provide additional sharing permissions. OnlyOffice ( • Can fill forms • Can review • Can comment • Can print (would be covered by hide download) • Can download (would be covered by hide download) • Can edit (would be covered by regular permissions) Collabora has quite fine granular options to set (DisableCopy, DisableExport, HidePrintOption, HideSaveOption, HideExportOption, UserCanWrite) but I think we do fine by just using our current hide download/read/write permissions for those. However in the future there also might be options similar to the ones in OnlyOffice. Edit: It should be possible for apps to limit the availability of permissions like Additional options that might be possible for link shares: • Watermark file (only makes sense for hide download links, as otherwise yo…