[#3524] Ignore family members without BSN

[SilviaAmAm]

Fixes #3524

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (df68b79) 95.97% compared to head (4db05df) 95.97%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3561   +/-   ##
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  Coverage   95.97%   95.97%           
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  Files         679      679           
  Lines       21840    21844    +4     
  Branches     2519     2521    +2     
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+ Hits        20960    20964    +4     
  Misses        610      610           
  Partials      270      270           

Files	Coverage Δ
src/openforms/contrib/haal_centraal/clients/brp.py	100.00% <100.00%> (ø)

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[CharString]

It's fine, so I approve, just a remark and a question:

• The v2 mocks return a different response for essentially the same call to the same endpoint. If I understand correctly, the real endpoint response would always contain both children and partners. I'd try to avoid these kinds of mocks that assume a certain implementation. In this case it never tries to reference the partners key if they aren't requested. For instance: a refactor of the implementation that always processes everything from the api response and only filters just what's being asked in the answer, would work against the real api, but trigger these tests. (contrived example, but in essence, I like be able to refactor without changing the test suite and have the tests as a canary in the coal mine to detect when I broke something)

• Is just mentioning the omission of people without BSN is enough information for a form designer to be able to cater for these cases? Do we need to give examples or suggestions, like a repeating group for "missing familiy members"? I guess they already have to deal with submitters that have no BSN themselves and when the BRP services are unreachable for some reason.

[sergei-maertens]

• Is just mentioning the omission of people without BSN is enough information for a form designer to be able to cater for these cases? Do we need to give examples or suggestions, like a repeating group for "missing familiy members"? I guess they already have to deal with submitters that have no BSN themselves and when the BRP services are unreachable for some reason.

They definitely can't cater for these cases, but to be able to do that they're going to have to tell us how they expect to handle that. I think we have too little domain knowledge and attempts to get that knowledge from actual teams building forms have been unproductive.

[sergei-maertens]

My sausage fingers accidentally closed the PR, sorry!

[sergei-maertens]

Please rebase on master to sort out the CI failures