How to automate the installation from ISO?

I try to perform unattended installations of Ubuntu 20,04.05 using the "ubuntu-20.04.5-live-server-amd64.iso" iso.

Due to the absence of the `boot_command`, there seem to be no way to influence how the installer is started from the iso.
Adding `userdata` with "#cloud-config/autoinstall" has no effect on the Subiquityinstaller, if there is no possibility to tell Subiquity that it should be used and where it can be accesses from..

Oddly, the `boot_command` is mentioned in the description of `http_directory` and `http_content`, but it doesn't seem it is implemented for the CloudStack provider.

What am I missing here? How do we make the CloudStack provider use userdata for Subiquity, preseed.cfg for Debootstrap or kickstart. ks for Kickstart?

首先跟踪 CloudStack provider 对 http_directory、http_content、userdata 以及缺失的 boot_command 入口点的处理方式。比较所请求的 Subiquity、Debootstrap/preseed 和 Kickstart 流程，然后在实现之前定义每条无人值守安装路径所需的 provider 行为。

由索引模型根据 Issue 内容生成。