At dev time, use ng build --watch to build the angular app.
This outputs to target/classes/static, which Spring Boot will
automatically pick up at runtime.
In prod, we assemble using a different strategy, to keep build times low.
Instead, the web app is built in parallel to the main java app.
Our docker build combines the two (see Dockerfile), and configrures
the spring boot app to serve from opt/service/webapp