Trying out a maven-plugin version.

[mihxil]

It is possible to build the docker image using maven plugins. This may be convenient for java-developers, and we may also assume that maintainers of such plugins have good ideas about how such a thing should look like.

The springboot maven plugin itself even supports creating docker image directly. I'm not entirely sure I like that, one, but there are also alternatives like 'fabric 8' and google's 'jib'.

Actually from the point of view of gha this is a simplification. It only needs to call mvn. There is generally no need to 'deploy' the maven artifacts (jar/war) to a maven-repository any more, because if a project can be wrapped in a sensible docker image it is likely an 'end product'. But if needed, I say that the called maven target should be configurable. Or, we could just leave it open in the gha, and depend on mavens 'defaultGoal' entirely.

At least one or two of the plugins I tried, even understood ecr, and pushed themselves. But we could also make them build to local docker only, and add a docker push in the gha, if that is for some reason needed or desirable.

This would also fix #69

because the docker address will be completely left to the maven plugins itself.