refactor code to replace `map[any]any` with actual struct which represents docker-compose manifest

[n0npax]

trafficstars

dealing with map[any]any and casting particular fields to particular types doesn't seem to be the best solution. It would be nice to use some structs to manage docker-compose manifests in more organised way.

[krzko]

Would definitely love to do this when time allows. Would prefer to attack this when it gets refactored into a package so you can run custom stacks.