I don't know why but this was not problem until I switched to Dancer2
which (or Config::Any) warned me during first runtime that YAML is
deprecated and I need to install YAML::XS.

Either the XS version or something in Dancer2 is more strict.

No big deal (yet?)...

It's not possible to allow arbitrary paramers if `params()` is used,
since in cases of route matching, this hash will always contain
key `splat`.

https://github.com/PerlDancer/Dancer/issues/909

Using `request->params('query')` leads to clean params reflecting query
in URL.