Pypdns

Using [cached_property](https://docs.python.org/3/library/functools.html#functools.cached_property) in a class with `__slot__` is not possible, this release fixes that.

Also adds a test suite.

**Full Changelog**: https://github.com/CIRCL/PyPDNS/compare/v2.2.1...v2.2.2

Maintenance release, strict typing, update dependencies.


**Full Changelog**: https://github.com/CIRCL/PyPDNS/compare/v2.2.0...v2.2.1