failsafe mode

[fabricedesre]

There are cases where we panic!(), like https://github.com/fxbox/taxonomy/blob/674b72d5d7b6eb53f1010a0048d4c4e9f4afcb58/src/tag_storage.rs#L53 because we don't have a good way to recover.

One solution to deal with this kind of situations can be to not panic, but instead to restart the foxbox in "failsafe" mode, in which we only do the bare minimum, safe things with some diagnostic to help fix the issue.

[Yoric]

In the Taxonomy back-end, I use a macro log_debug_assert! that causes a panic in debug builds and just logs in release builds. I think that it's an acceptable solution for many things.