Add more logging

[wilzbach]

I am having a really hard to to see whether everything is work as supposed.
In any case, logging is cheap and it's better to have the history in case something didn't go as expected ...

[dlang-bot]

Thanks for your pull request, @wilzbach! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.

Some things that can help to speed things up:

• smaller, focused PRs are easier to review than big ones

• try not to mix up refactoring or style changes with bug fixes or feature enhancements

• provide helpful commit messages explaining the rationale behind each change

Bear in mind that large or tricky changes may require multiple rounds of review and revision.

Please see CONTRIBUTING.md for more information.

[wilzbach]

This is would be very helpful now (and it just adds a couple of log messages) -> merging.