Fixes from the review of api.files:
- `files.attach` to a new draft runs `onBeforeAttachmentUpload` for each
file and the server's total size limit before `compose.open`, which
runs neither; refused files come back in `refused`
- a write is refused when a folder above the target is missing from the
listing, instead of counting it as not shared
- `onFileMove` reports the item as it was, from where it was, like the
Files app's own move
- writes are counted against the 20-a-minute limit before the drive is
listed, so refused writes count and cost no listing
- reads stop the download past 20 MB (`fetchBlobArrayBuffer` with a
limit) and answer `too_big` when the listed size was wrong
- when the server refuses the new content of a replaced file, the old
version's copy is taken out of the trash again
The two getText assertions on `fetchBlobArrayBuffer` now expect the
account (undefined for the own drive) and the byte limit, since the
call passes both.
Linus Rath
cf512f0a4e