ENH: Second and Third Pillar Pensions - Taxation and Sozialversicherungsbeiträge

[MImmesberger]

Is your feature request related to a problem?

#1029 added three basic types of pensions: geförderte / reguläre private Rente and Betriebsrente. Also, we implemented the very basic rules regarding social security contributions and taxation of those types of Einnahmen. However, only the state of the law of 2025 was implemented.

Describe the solution you would like to see

We should cover reforms as well (there was one in 2018 I believe). Presumably many more since the 2000s.

[MImmesberger]

#1093 fixed this for the most part.