How to specify the domain app when generating a new app inside an umbrella project?

I’ve created a new umbrella project
mix my_app --umbrella
so I got the umbrella folder with the two usual apps (one for domain, the other for web interface ),
apps/ my_app
now I want to add the API frontend and I’m about to try
mix my_app_api --module MyAppAPI --no-html --no-webpack
but I realise that, AFAIK, there are no options to specify, on the command line, which should be the domain app that manages the repo, so if I give the above command I’ll have to search and edit all the generated entries (from MyAppAPI.Repo to MyApp.Repo), or add everything it is needed by hand if instead I use the --no-ecto option.
I’m wondering if there is a way to avoid all these, small but annoying, “by hands” operations when add a new app by the mix task.