Ubuntu server subiquity autoinstall

[Tom H]

I've deleted the emails of "Does kickstart work on 20.04 LTS", so I'm
breaking the thread. Sorry.

There's an example of patching an ISO on [1] that seems to imply that
the autoinstall file has to be called "user-data".

It makes sense given that this is the name that's used in the seed.iso method.

"user-data" must override the equivalent data in
"/etc/cloud/cloud.cfg" and "/etc/cloud/cloud.cfg.d".

[ The kernel cmdline is sed-ed in both "/boot/grub/grub.cfg" and
"/isolinux/txt.cfg" to include the "ds" and "s" values. ]

[1] https://gist.github.com/s3rj1k/55b10cd20f31542046018fcce32f103e