BUG: Full retirement age Rente mit 63

[MImmesberger]

Bug description

I stumbled on the calculation of the full retirement age and I think it is wrong. In the parameter file we have:

altersgrenze_besond_langj_versicherte:
[...]
  type: piecewise_linear
  2012-01-01:
    0:
      lower_threshold: -inf
      upper_threshold: inf
      rate_linear: 0
      intercept_at_lower_threshold: 65
  2014-07-01:
    0:
      lower_threshold: -inf
      upper_threshold: 1949.5
      rate_linear: 0
      intercept_at_lower_threshold: 65
    1:
      upper_threshold: 1951.5
      rate_linear: -1
    2:
      upper_threshold: 1952
      rate_linear: 0
    3:
      upper_threshold: 1964
      rate_linear: 0.16666666
    4:
      upper_threshold: inf
      rate_linear: 0

The 2012 rule seems to be correct but the 2014 rule should give a full retirement age of 63 until (and including) birth cohort 1952. Then the full retirement age increases as specified in § 236b SGB VI.

[MImmesberger]

Just realised that this is due to the same reason as #665. Our current implementation does not depict retirement ages correctly for older birth cohorts because we do not distinguish between different policy environments. Rather, GETTSIM yields the statutory retirement ages that people actually faced when making their retirement decision (based on birth cohort but not on calendar year -- as if the retirement system didn't change over time).