Resolve issues with sonar analysis in forks

It seems that the sonar check fails on forked branches. We should either specifically deactivate it there or find a workaround.

As mentioned by @krmahadevan:
#63

Start by reading issue #63 and tracing how the Sonar check is configured for forked branches. Done means forked-branch analysis no longer fails, either because the check is safely disabled there or because a documented workaround makes it pass.

Written by the indexing model from the issue text.