BUG: fg_id creation sensitive to order of adults

[MImmesberger]

Bug description

@JuergenWiemers drew my attention to the fact that our endogenous fg_id creation is sensitive to the order of adults in the data.

Consider the example input below. This is a 3-person household (parent + child and other adult in an Einstandsgemeinschaft with the parent). Note that the order of people in the household is a bit peculiar: First the childless adult, then the child, then the parent. Here, we would expect:

  fg_id:
    - 0
    - 0
    - 0
  bg_id:
    - 0
    - 0
    - 0
  eg_id:
    - 0
    - 1
    - 0

The result, however is:

  fg_id:
    - 0
    - 1
    - 0
  bg_id:
    - 0
    - 100
    - 0
  eg_id:
    - 0
    - 1
    - 0

This is due to the loop in our fg_id algorithm. There, the algorithm loops over p_ids in the data. For a given p_id, the loop starts with a candidate fg_id, assigns this fg_id to the current p_id, its Einstandspartner, and its children. The candidate fg_id then increases by 1 and the loop continues with the next p_id that does not have a matched fg_id yet.

The problem in the example below is that, the loop does not recognise the child as an fg_id member. In the first iteration, it assigns fg_id 0 to the first and last adult (Einstandspartner), but at this point, it does not know that the last adult has children in the household.

From what I see, this is also not solved by sorting the (internal) DataFrame properly in more complicated family structures (e.g. 2 adults and 2 children, each child is from a different partner).

Example Input

---
info:
  note: ''
  source: ''
inputs:
  provided:
    p_id:
      - 0
      - 1
      - 2
    alter:
      - 39
      - 13
      - 42
    hh_id:
      - 0
      - 0
      - 0
    p_id_einstandspartner:
      - 2
      - -1
      - 0
    p_id_elternteil_1:
      - -1
      - 2
      - -1
    p_id_elternteil_2:
      - -1
      - -1
      - -1
    eigenbedarf_gedeckt:
      - false
      - false
      - false
outputs:
  fg_id:
    - 0
    - 0
    - 0
  bg_id:
    - 0
    - 0
    - 0
  eg_id:
    - 0
    - 1
    - 0