Install debian on encrypted volume

See https://www.blakecarpenter.dev/installing-debian-on-existing-encrypted-lvm/ The main points:

- expert install
- "Load installer components from CD. From here, you want to select crypto-dm-modules and rescue-mode."
- ctrl+alt+f2 to jump into a shell
- depmod -a
- cryptsetup luksOpen /dev/sda3 debian-crypt
- vgchange -ay
- ls /dev/mapper
control debian-crypt debian-home debian-root debian-swap
- "Hit ctrl+alt+f1 to return to the Debian installer and continue to Partition disks. Select Manual."
- setup partitions/mount points
- stop before Install the GRUB bootloader to a hard disk. ctrl+alt+f2 to jump into a terminal.
- blkid
- nano /target/etc/crypttab
debian-crypt UUID=98...eaa none luks
- "Continue to the end of the installation. When the generating initramfs step appears, the image will be built using the crypttab file you just modified."