Date arithmetic does calculate correctly +/- 1 month

[seflue]

Describe the bug

If I add a month to the 31st of a long month (January, March, Mai ...), the Date overshoots one month. This was exposed by using :end_of('month') and :add({month = 1}) and :subtract({month = 1}) in Calendar.

Steps to reproduce

See tests in attached PR.

Expected behavior

Adding a month to 31. of a month should give me the last day of the next month. This also means correct handling of leap years.

Emacs functionality

No response

Minimal init.lua

Empty on purpose

Screenshots and recordings

No response

OS / Distro

Linux

Neovim version/commit

0.10

Additional context

No response