don't automatically delete drive files if they're used by something
after !589 (merged) and 5f7fc54e we automatically delete a drive file that was used for a custom emoji, when the emoji is deleted or its file is changed.
but it's possible to use the same drive file for multiple purposes: I can upload it once, then attach it to a note, use it as my avatar, and also a custom emoji. Unlikely, but possible.
In those cases, we should not delete it automatically!
Add a DriveService.deleteFileIfNoLongerUsed()
that checks if the file is referred to by note.fileIds
, user.avatarId
, user.bannerId
, user.backgroundId
, channel.bannerId
, page.eyeCatchingImageId
(maybe others?), and doesn't delete the file if so.