Add integration tests using docker to our github actions.

[bnouwt]

From issue #495 we learned that parts of our stack need additional tests to prevent bugs to go unnoticed into our binaries (jars, docker images). Our current automatic testing happens mainly within Java Unit Tests, but not all bugs (looking at your #495 ) are detected. A simple test of just starting our docker images and see if they keep running for 5 seconds without exiting would have prevented #495 .