According to RFC 7230, URLs can be up too 8000 characters long. Resize
all URL fields accordingly.
Also, add a test to verify that URLs with more than 8000 characters are
rejected by the update hook.
Reported-by: Andreas Linz <klingt.net@gmail.com>
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>
