Still, it seems unusual to not be able to run a set of commands on initialisation.
I haven't looked at Docker in a long time, but isn't there something called an entryscript? I'm not sure I'm remembering the name correctly -
- yep, entrypoint script not entryscript.
I remember something about setting up Wordpress in Docker and the official docker image has this type of script that initialised the database just once.
Might be worth looking into just for interest (maybe not for fixing this 'issue' as you point out its cheap to get a 3 year cert). I imagine one time init commands would be useful to have in their own right anyway.