Bundling scripts (mix ecto.setup etc) with new elixir releases

So I actually read the docs properly - and there is some description given to adding custom tasks -https://hexdocs.pm/mix/Mix.Tasks.Release.html#module-one-off-commands-eval-and-rpc

What I’m wondering though, is what’s the idiomatic way to package them up nicely with the bin/ init script? Is there a standard extension point?