Use diamond operator whenever possible.

Try a different docker image that apparently does not have SSL issues. See https://github.com/docker-library/openjdk/issues/145

Go back to 1.3.2 since more recent versions do not seem to work on GitLab CI for obscure reasons (works locally).

GitLab CI complains and fails with "the trustAnchors parameter must be non-empty" when using 1.6.0. Try a less recent version of the plugin.

Add another dimension of genericity to the elements of the metamodel corresponding to interfaces to support contingency.