Looking at your structure, I guess You use mix new ... --umbrella, then go to apps and build phoenix app.
But there is also another way of doing this
mix phx.new hull_cinema_club --umbrella
After, You build the movie_importer, You will get this structure
WIth hull_cinema_club acting as core. I tend to prefer this, as it simplify struct a little bit, as there is no need to build phoenix_app and hcc_core by hand. And also, the web part is configured only for web. While the core is the db part.
Also configuring tests is automatic, while in your case, You will need to make it by hand.
It's just a matter of taste, I used the same structure as yours before...