Comment 10 for bug 1980018

I see that @gmazyland was saying there are two ways to implement this and neither is 'cryptsetup'.

Having got it working, my solution requires modification to two files which are packaged in `cryptsetup` and `cryptsetup-initramfs` in Ubuntu, and adding one file to `/etc/initramfs-tools/hooks` (or the platform equivalent location)

I've generated minimal patches of what needs doing in my repo under the 'patches' directory.
  https://github.com/wmcelderry/systemd_with_tpm2/tree/main/patches

and the extra hook script is under 'scripts':
  https://github.com/wmcelderry/systemd_with_tpm2/tree/main/scripts

I'm not claiming these are the best way to implement the solution, but it makes it very clear what I have done to get it working.

If there's a better way to implement this, I'd love to hear your thoughts and integrate it.