Move `Bash if-else-statements` out of the Dockerfile generated, and into the generator

[KTanAug21]

What:
To make the Dockerfile smaller, can we move bash statements out of the Dockerfile generated, and into the generator?

https://flyio.slack.com/archives/C042W39VAMB/p1710508019502139

Reason:
"...makes the Dockerfile smaller and easier to understand."