This is a bootstrap-type project to get a spring-boot application to run locally using dev app engine.
App Engine in the cloud (flex) can run a jar OK.
Dev app engine demands a war! See https://docs.spring.io/spring-boot/docs/current/reference/html/howto-traditional-deployment.html on how to produce a deployable war.
Install Google Cloud SDK: https://cloud.google.com/sdk/
mvn appengine:run