"date" is reserved for the last-modified-timestamp of each file
if extraction of the audio metadata property "date" was enabled
(not default), this would have collided; rename the audio prop
discovered thanks to #1053
uploading a folder named COMPLE:X into exfat on linux would fail
because exfat behaves like windows, rejecting <>:|?*"\/
this would also fail on windows, but then due to
sanitize_fn being overly aggressive
fix this by detecting filesystem traits on startup and
also translating vpath early on windows
plus these fixes:
* adds a previously missed libvips optimization,
giving much smaller files at the same quality
* try to align the quality-scale of each backend
(pillow, libvips, ffmpeg) by filesize
on Windows and Macos, most filesystems are case-insensitive,
which can lead to dangerous situations
one example is when another program (not copyparty or its UI) wants to
rename a file from `Foo` to `foo`; the program will probably start by
checking if `foo` exists and then delete it, however this would match
`Foo` and confuse the program into deleting the wrong file
fix this by adding a VERY EXPENSIVE detector to prevent this,
by listing the parent folder and checking if the case matches
this check will auto-enable when a case-insensitive FS is detected on
startup, but option `casechk` (global or volflag) can override this
extends idp-auth to also accept a collection of headers (and
expected values of those headers) and map those to certain users
useful for Tailscale-User-Login and similar
