Outdated graphviz version creates problems

[ascheman]

The current version of the docToolchain Docker image (2.0.1) contains an old version of graphviz (2.40.1) which is known to cause problems, cf. https://forum.plantuml.net/5459/too-much-vertical-whitespace-when-using-packages.

Please update to a more recent version (which should come automatically when switching to a current openjdk:17-jdk-alpine base image (PR is coming, stay tuned, @rdmueller + @aklemp).

[ascheman]

Upgrade is not straight forward, since it first requires upgrade of docToolchain to Gradle (Wrapper) 7.x, cf. docToolchain/docToolchain#662 (-> waiting for a new version to be assigned, when docToolchain/docToolchain#663 is merged).

[ascheman]

Found an alternative by using the openjdk/15-jdk-alpine base image - it contains at least GraphViz 2.44.0 😄